> Daytrip to Canterlot
>  by SplatterPhoenix
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> Train Ride
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Visiting Canterlot and going on a palace tour had been Berry's idea. Derpy had been surprised, since she hadn't imagined that her lover would much enjoy the place. The earth pony didn't particularly care about other ponies, particularly not ones that put on airs. She'd be happy to spend the weekend at home with their daughters rather than square the younger two away with sleepovers. Amethyst Star, at least, might enjoy the novelty of having the house all to herself.

Of course, they'd been in a relationship for long enough that it hadn't taken Derpy much to realize that she'd probably be providing all the entertainment Berry would need. The earth pony enjoyed seeing Derpy all hot and bothered, and having her huge, milky tits paraded in front of strangers who hadn't had a chance to get used to them would make it very difficult to keep her composure indeed.

Derpy loved being seen. Her tits were amazing, they needed to be shared, and she was glad every day that they were now large enough that even when she technically kept them covered, they were impossible to hide. Fortunately, her job as a mailmare kept her moving around in public every day for people to appreciate. Better still, every landing was practically a lewd act, sending her great rack bouncing and wobbling.

She'd milked herself intensively during her morning shower. It wouldn't keep the arousal at bay, but it'd probably at least get her through the train ride without some milk-related accident.

Derpy had taken a window seat, Berry sitting next to her. She'd been a little disappointed to be able to board the train without her breasts touching either side of the door, and her tits only filled her lap if she slumped forward, adopting a rather poor posture, but that would change in the near future. While her rack was wider than the rest of her and already brushed against the wall, she could easily imagine larger breasts invading her partner's personal space. Berry would probably fondle her sneakily if her arm was hidden behind a massive boob.

Just thinking about Berry's hands on her breasts caused Derpy's nipples to grow erect. They were the size of shot glasses, kind of big even on her huge breasts and impossible for her cheap t-shirt to hide. Two major parts of Derpy did not like feeling in any way contained or restrained at all. She went topless at home and while she hadn't made a study of it, she felt that she required fewer masturbation breaks compared to her work hours in full mailmare uniform. Part of that was likely the lack of an audience to rile her up, but she also imagined herself bursting out of her top in a tide of milk and titflesh much less frequently when she wasn't wearing one.

Derpy tried to avoid such thoughts. It would be easier if they had any of their daughters along, her great boobs were always at their most cooperative when she was paying attention to their children, because being a good parent was more important than her personal indulgences. Naturally, Berry had planned the trip just for the two of them because they'd both enjoy Derpy's efforts to control herself, as well as her eventual failure.

She closed her eyes, trying not to notice how other passengers looked at her chest. Every so often a shiver of delight radiated from within her breasts, as though they independently felt the gaze of onlookers brush across them. "What do you think Sparkler is gonna do alone at home?" Derpy tried to distract herself.

"Hm." Berry huffed, apparently amused. "Sit in my recliner while she reads? We got a boring daughter."

"Well behaved," Derpy corrected her with a smile. Their oldest daughter had been a headache just after the adoption, presumably to test if they'd send her back into the foster system when she became inconvenient, but since then, Sparkler hadn't made waves and she obviously enjoyed being a big sister. "Glad you connect so well."  

Berry, like Sparkler, hadn't had a great childhood and it had been something for the both of them to connect over. Both also seemed perpetually touch-starved, and though they hid that in public, they enjoyed cuddling with Derpy and the younger daughters. That trust and tenderness always filled her with immense happiness and satisfaction, more than enough to sooth the usual demands of her body for the duration and some time afterwards.

"Mm." Berry made a noise of agreement. "She's worried we expect her to move out as soon as she's done with school. Hasn't gotten to enjoy our home for as long as the younger girls will have."

Derpy had been a restless youth, wanting to see the world outside of Cloudsdale, and leaving her home town had been a huge relief to Berry, so they weren't well positioned to understand how their daughter felt. Still, if Amethyst Star felt she wanted a few more years of a stable, loving home life to make up for her first decade or so of her life, Derpy wouldn't complain. "You told her that we won't?"

"Yeah."  

They passed the time with more idle conversation about their kids, which always was a reliable way to spend time without becoming hornier than she already was.

Of course, Berry just had to betray her. She would hardly have proposed the trip for just the two of them if she wasn't going to try and torment Derpy innocuously.

"By the way," the earth pony started idly, "I brought a couple changes of clothes, just in case of an eruption."

Derpy sucked in air as she flushed with further arousal. To the ears of other nearby passengers, it had probably sounded like a reasonably pragmatic statement. Some ponies blushed, obviously assuming now that her exceptional breasts lactated. Her fat nipples, still erect, throbbed so insistently it had to be visible to anyone looking at that moment. Derpy hoped that it created the impression that her nubs were reaching for hungry mouths.

Bringing extra shirts was, of course, thoughtful of Berry. But the important part was that contemplating the inconveniences of Derpy's tits and planning around them was incredibly hot. Of course her great glands were so monstrously fruitful that staining her shirt was inevitable. Derpy had become almost incapable of embarrassment or shame when it came to her body. She dreamt of the day her rack would be large enough to leave her stuck in a door somewhere public.

A bit of particularly uneven track sent a jolt through the train, making her boobs jiggle. Celestia, they were so soft. Derpy didn't understand how they could be so beautifully soft to play with while retaining their proud shape unaided. Perhaps whatever magic made them so excessively bountiful also ensured that they were pleasant in every particular for her and Berry?

They sloshed audibly, something Derpy would never get tired of.  As far as her understanding of anatomy went, boobs didn't have some interior space for milk to splash noisily around in, so the sounds were clearly a delightful way for her body to communicate and draw additional attention.

Derpy willed her breath to remain steady, adjusted her position slightly, then closed her eyes again and allowed herself to enjoy the increased warmth between her legs and the slow waves of pleasure washing over her thoughts. She'd learned to enjoy the ride, to enjoy the way she always wanted to touch herself and be touched, wanted Berry to play with her amazing tits. Derpy couldn't recall how it felt to not be horny. Over the years she'd become accustomed to it. It was her new normal. Besides, she had unlimited milk on tap, so being always down to fuck didn't even compare in terms of weirdness.  

Maybe another pony who hadn't been changed by her magical rack might feel perpetually unsatisfied? As far as Derpy was concerned, there just was never too much of a good thing, especially not when it came to Berry making love to her.

It was inevitable that her lust would continue to escalate today. Her thoughts would grow fuzzy and sluggish, although slowly. Derpy had, after all, a lot of experience with her unrelenting libido. Even under normal conditions she'd inevitably encounter sights or thoughts which would excite her further, without Berry going out of her way to tease her.  

The earth pony leaned against Derpy. Being the taller mare made it easy for Berry to talk quietly near Derpy's ear. "Lots of people are gonna be telling their friends about seeing you. Don't know how many are gonna believe them, yeah?"

Derpy hummed, smiling lazily. Her amazing breasts were no real burden to her and she always dreamed of being larger, so it was nice to be reminded that her rack was already staggeringly large and impossibly well-shaped by the standards of any other pony. They'd probably each be over a foot across at their widest point if their great heft didn't form a beautiful natural cleavage. They retained an attractive, pert shape, jutting proudly rather than hanging heavily, which she couldn't explain in any way other than magic, and which was the only reason they weren't resting in her lap quite yet – she was nearly there. There was just enough sag to make them seem natural as long as observers didn't think too hard about it, and they needed no real support. Despite their improbable ability to retain their shape, they were enticingly soft to the touch whenever they weren't engorged with milk.

"Still," Berry added, "I guess they're not going to talk about having seen the milkiest jugs ever." Somehow she made that sound like a regrettable missed opportunity.

"I don't want to pay for clean-up, Berry," Derpy huffed, pleasure pulsing from her breasts. They were clearly eager to demonstrate to all and sundry what they were capable of. They felt so alive, especially in moments like this. She became more acutely aware of her output. Derpy's great glands hadn't ceased production since her pregnancy, when their size had still been wholly unremarkable. She knew with absolute certainty that she could never give as much milk in any span of time as she produced, that every time she allowed herself to gush uncontrollably, she'd end with the amazing feeling of being fuller than before.

When her mood was right, she thought she could feel every drop of milk she hadn't shared in the preceding years, oceans of it with no use or existence beyond the exhilarating knowledge of being the most bountiful creature alive.

Derpy knew that Berry favored a supernatural explanation. Her boobs were already clearly magic, so it would be pretty boring to assume that Derpy had just latched onto some delusion to make her ability to produce impossible amounts of milk on command more complex than it was.  

Were Derpy's boobs bigger on the inside? That was fun to contemplate whenever Berry sank her fingers deep into her yielding flesh. Or perhaps there was some kind of milk dimension of infinite capacity she'd been connected to in some cosmic accident.

Clearly, her magic boobs were a force for good. Derpy never felt compelled to feed anyone more milk than they were interested in, and although she needed sexual and lactic release regularly and frequently, these requirements had never gotten in the way of her family's emotional needs. Despite this, sometimes it pleased Derpy to imagine that her heroic tits were holding back some callously indifferent force of endless vitality, her plump nipples keeping the world safe from an apocalyptic deluge.

Still, her boobs were wilful. She'd never want to force her milk on anyone, but her exhibitionist side dearly wanted everyone to know that the option was available. She felt an intense, pleasurable churning in her breasts, and she imagined the sea of her milk reserves being unsettled by the storm of her lust. Derpy had to bite back a moan, drawing on her years of experience being a functional adult despite feeling tremendously horny.

Berry, of course, loved how easily her words could rile up Derpy and her breasts. "Knew why I brought extra shirts," the earth pony commented as the first fat dollops of milk escaped Derpy's control and began soaking her shirt. She wished there was a mirror nearby, as the sight of a thin shirt clinging wetly to her large nipples was tremendously enticing and best viewed frontally.

Derpy clucked her tongue in faked disapproval. "I'm gonna be horny as hell by the time we arrive," she informed Berry, keeping her voice pitched so only the nearest ponies would hear and assume she had spoken too loudly unintentionally. "You know it'll be a mess if I bring myself off while backed up, too." She rubbed her thighs together. Imagining herself spraying milk in front of a crowd of perfect strangers only made her arousal worse. She'd decided on a skirt of modest and sensible length today, and she was pretty sure hardly anyone would notice if Berry would just sneak a hand under her tits and past the skirt's waistband. She'd need bigger tits to make absolutely sure it could be done without anyone noticing.

Instead, Berry just took Derpy's hand into her own. Much tamer than what Derpy had been thinking about, but she wasn't going to say it was worse. The earth pony also gave her a brief, questioning look. Derpy knew that the other mare would stop trying to work her up if she asked. Of course, her boobs were already stirred up, aching for release, and Derpy badly wanted to feel Berry's hands on her tits, maybe her teeth gently nibbling on her stiff nipples.  

That wouldn't just go away even if they spent the rest of the train ride chastely holding hands. Derpy would need release either way. Besides, their lives weren't without stress, so having some real fun when it was just the two of them was really just proper self-maintenance. It'd also be a terrible waste to hide in a bathroom somewhere to milk herself to a quick climax when there were all these strangers to amaze and astound with the fantastic excesses of her body.  

She shivered with raw need, biting her lip and giving Berry an encouraging nod to signal that she was ready to make a splash.

"Y'know," Berry muttered in response. "I've always appreciated how responsive your jugs are."

Derpy liked that as well. It was beautiful to hear fantasies of her own continued growth voiced by another. "Well, you're supposed to enjoy them."   

"I do," her lover agreed. "Kinda wonder if it goes beyond making you randy. Y'mind if I try makin' a request?"

"You know I trust you." In fact, Derpy was quite happy to play along. The big earth pony was pretty trivial to satisfy sexually, but could get creative with the ways she drove Derpy wild just by talking about her boobs and how big they might get. She couldn't imagine what Berry might ask of her, but surely her boobs would play along to please the other mare.

Berry shrugged. "I was just thinkin' it'd be fun if you got stuck in the doors while getting off the train. If your rack was that wide, I could stand behind you and really sink my hands into them as I push, while you'd make ponies scramble not to get hosed down with milk on the platform, yeah?"

"Mhm. Lovely idea," Derpy agreed, breathily. The idea of being so big that it got inconvenient for the people around her was really doing it for her. Her great breasts throbbed in anticipation, as she'd had that very thought when she entered the train.

"Well, I don't feel like waiting," Berry stated with a grin. "I want that today. Not askin' for anything permanent, but you can't tell me these jugs aren't magical enough for a bit of fun." The taller mare lowered her voice further. "C'mon, Derps. Grow for me."

Derpy bit her lip as she felt her body react to Berry's words. Her fat nipples twitched and her boobs seemed to jiggle with internal tremors, set to some languid rhythm, like the beating of two great hearts. Each one was accompanied by a shockwave of pleasure crashing through her. It was becoming increasingly difficult to pay attention to anything but her tits and the feel of Berry's hands on her own.

She felt overwhelmed by impressions of rushing liquid and knew her glands frantically increased their output. Although Derpy had somehow managed not to cum on the spot or even moan too loudly, she couldn't stop herself from giggling with sheer glee when she felt the already great weight of her rack increase and the bulk of her left tit shift as it grew and fought for space against the wall.

"It's w-working!" Derpy grinned. Physical pleasure aside, it simply delighted her to know how far her body could go to please Berry. She didn't feel the blissful contentment she'd come to associate with new permanent growth. This, clearly, would purely be for the sake of pleasure.

With her huge, growing tits finally sitting solidly in her lap, Derpy enjoyed the way her knees pressed into their undersides. As her right boob encroached further into Berry's personal space, the bigger mare muttered something warm and approving in Derpy's ear, although her raw need was making verbal communication difficult. She was more aware of every inch of titflesh and the endless milk roiling and churning within than of her surroundings.

Another pony would long since have climaxed, and it wasn't actually difficult to get herself off in a hurry during a lunch break or something, but as much as Derpy's breasts were unique and still growing, so were the dizzying, helpless heights of arousal she could achieve with the proper patient ministrations and enough time.

Derpy tried to hold still, trying not to accidentally tip herself over the edge and start cumming before their arrival, but her tits were growing so damnably sensitive, she felt every shift of her flimsy shirt across her skin as the top started straining against her mass. Despite their increasing weight they remained firm, fat and round. Seated as she was, their upper slopes rose to take up more of her lower field of view.

She felt one of Berry's hands on the underside of her right breast, which already half sat in the earth pony's lap anyway. Derpy wondered what it said about her that she could hardly pay attention to the world around her as she struggled not to start groping herself, but could feel everything happening to her tits with exacting clarity as Berry traced letters on her skin.

Derpy was pretty sure she felt Berry spell out 'Love you' and the secret nature of that display of affection made her giggle again before she pressed a kiss to Berry's cheek. Of course, she recalled pretty clearly that her lover had originally joked she'd have to communicate that way once Derpy grew vast enough that most of her rack was too far from her ears for talking or shouting. Her breasts always throbbed in warm approval at such fantasies.

The rest of the ride was a blur to Derpy. At least once a concerned sounding pony talked to them, and Berry replied smugly before the other pony left, flustered. Maybe Berry had exclaimed that Derpy was just monstrously horny. Mostly Derpy just stewed in the feeling of raw potential, straining to be released. Berry's proximity and the earth's pony's steady breathing allowed Derpy to maintain control. The other mare wasn't audacious enough to nap after priming her to make a mess, but having the big mare relax against her body was fulfilling to Derpy even while she felt such desperate need.

When the train finally stopped, Berry had to help pull Derpy up from her seat after grabbing her backpack, although she managed to stand on her own afterwards. They were both well-suited to handling Derpy's boobs, Berry was strong because she was an earth pony, and Derpy was strong because she was built to have immense tits.

Less well suited to handling Derpy's boobs was the interior of the train car. Although her shirt yet lived, it had survived only by riding up until it covered nothing below her nipples, and there was no denying that her rack was much wider than it had been at the start of the journey, extending further ahead of her and hanging lower than before. She'd been looking forward to being truly too large to easily navigate normal pony places for years, and the realization of the fantasy instantly shattered her self-control.

Electrifying pleasure sent a tremor through her body as Derpy felt herself bump into and drag past the back of another seat. She came with a quiet moan, swaying on her feet momentarily. The release returned a modicum of clarity to her, but her tits were much too fired up now for a single climax to suffice. If she hadn't been so intent on making a scene the way Berry had described it, she'd already be gushing milk. As it stood, she felt herself growing engorged. If her nipples weren't so large and erect, her shirt would have long given up its hold on her rack.

Berry, walking behind her to help steady her, called out. "Best clear space on the platform! She's backed up enough to make a major splash!"

Derpy's bloated breasts sloshed noisily again, throbbing impatiently. The smell of her thick cream filled the space around her as the wetness around her nipples spread and milk ran down her exposed lower slopes. It had been a long time since Berry and herself had deliberately incited her urge to spread her milk around to such a degree. Much like her lust, it was a need which was most easily sated early and often in her day to day life.

Obviously, Derpy could have easily exited the train one big boob at a time. It would likely still have impressed anyone watching to see a pair of tits big enough to make it necessary, but it would have been the more boring option. Cramming herself into the open doorway was much more satisfying. She could probably have pushed herself through under her own power, but it was rare enough that Berry wanted to participate in one of Derpy's public spectacles.

She felt the exit's frame digging into her titflesh harshly, although her top suffered more from it, finally losing its hold and letting her impressive nipples go. If Derpy hadn't just wedged herself in place, her breasts would probably have dropped a bit and wobbled delightfully.

Derpy could see the passengers who'd disembarked before her push their way through the small number of ponies who'd planned to get on the train here. Those, particularly, were anywhere from puzzled to awed by the brazen display of her huge, immodest milk tanks. The first squirts of her milk arced to the ground.

"Make room, she's not gonna hold it in much longer!" Berry's second warning made Derpy grin smugly. She looked forward to crushing whatever mental images her audience was putting together, trying to predict what came next.  

Feeling the eyes of strangers on her naked chest, being impractically large, feeling full to bursting with milk, Derpy had expected it all. What caught her by surprise were the tight feelings at the cores of her breasts, the sudden urge to just grow and grow until she exploded out of her restraints. She'd never liked to wear much, but she hadn't expected her tits to react this way to more sturdy containment and couldn't wait to experiment more. Derpy came again. She moaned shamelessly as her control slipped and two long streams of milk splattered thickly onto the platform, mere hints of her abundance.

Much as she loved the situation, she planned to attempt something similar in private, because Berry drew the line at actually fucking her in public and Derpy herself wasn't feeling quite brazen enough to drop the thin excuse of her out of control breasts forcing her into making a spectacle. While Derpy's boobs and nipples could produce such spectacular orgasms that she didn't even need to touch her own sex, the idea of being completely naked while stuck like this as Berry pleasured her was exciting.  

Derpy felt powerful as her breasts grew, forced larger by the relentless pressure of her milk. She felt as though she really could outgrow her predicament, even though it wasn't wholly real. "S-so much," she gasped. "Help me, Berry."  She felt every detail of the material her breasts strained against, but there was no pain, and whatever slight discomfort she felt paled against the extraordinary sensations from within, more and more milk fighting for release.

She felt and saw Berry reach past her upper body on either side and place her strong hands on her tits, palms near the back, fingers digging into their sides. Derpy gasped joyfully. She'd recognize her partner's rough, calloused hands, that faded scar on her palm, even if she were being groped by a dozen people at once. Her bloated tits resisted at first, but Derpy practically felt the pleasure of Berry's touch radiate outwards through her body, when the feeling reached her nipples they trembled, twitched, and unleashed new torrents of milk, reaching further than her previous release.

Berry's hands and fingers sank into Derpy's newly yielding titflesh as the internal pressure decreased, and the earth pony's happy sigh by her ear brought Derpy over the edge to another climax, overcome with giddiness at another reminder that Berry enjoyed her amazing body as well. "Haah. They're a-all yours, Berry." The taller mare was playing along because it amused her to mess with people, but what she loved was getting a good grip on Derpy's boobs when they were soft and inviting. That Derpy loved having them handled roughly just made the two of them particularly compatible in that way.

"It's time," Berry warned her before a particularly firm squeeze, pressing in against her breasts and giving Derpy a firm shove from behind with most of her weight.

Derpy felt herself drag harshly past the door's frame as she slipped from Berry's grasp and stumbled forward, still pumping out milk. Her legs were weak from previous climaxes and Derpy fell to her knees in the puddle of her cream, then slumped forward onto her tits. She noticed a few spectators wincing at the rough landing. Derpy would have liked to reassure them, but telling them that the works of ponies could never hope to contain, let alone harm or slow her two unstoppable forces would just make ponies worry for no gain. Instead, she started massaging the flanks of her great breasts, from their bases in the direction of her nipples. Her glands felt even more alive than usual. Derpy made no effort to hold back moans as her tits surged larger and the force of her lactation redoubled, nicely measurable by how far her milk sprayed before splattering onto the platform.

"Alright folks, stay clear, don't blame us if you get wet." Berry herself made sure to stay either behind or at Derpy's sides as she addressed the remaining onlookers. Some had already gone off to board the train through other entrances, but there were always enough ponies who wanted to see the show to its end.

Derpy spent some time simply milking herself with increased force, which appeared to diminish her size again. "Hnng ......... I'm jus-just too small to hold it all," she whimpered. She could hardly go around telling people just how large she would grow in her fantasies, but she could at least imply that her current, plainly impossible, size was in some way insufficient.

Making a show of trying to get up, Derpy staggered a half step forward before dropping her weight onto her chest again, having succeeded in rolling forward until her nipples were trapped against the rough ground by her own weight, engulfed by the rest of her mass pressing against the platform. She keened wordlessly as another climax wracked her from the sheer joy of discovering a new sensation as her milk was forced out from underneath her flesh, bubbling forth in a froth by the sheer force of her lactation.

Berry drew attention to herself by unexpectedly responding to Derpy's words. "And I keep telling you," she made a very good show of sounding exasperated with a repeat argument, "volume going up faster than, uh, diameter is always gonna work against you if most of that volume is, is glands, yeah? You can't outgrow the problem!" Maybe she'd been reminded of that reality by some piece of homework their daughters had been doing. Whatever the case, Derpy could kiss the other mare for playing along and also for reminding her that her monstrous productivity was always going to increase faster than her size would.

"Uhm, should we look for a doctor?" It was a sensible question for the spectator to ask, and Derpy always appreciated ponies with a drive to help.

"Nah," Berry replied, unconcerned. "It's a known issue. Hormones or something. We know how to manage it and usually she gets through her days without ... this." She gestured vaguely towards Derpy.

Derpy was the centerpiece of a sea of milk by now, and she decided to act as though she was trying to do the sensible thing and aim herself at the edge of the platform so her milk wouldn't pool to such an extent before running down to the track bed. She couldn't stop herself from hoping that her display would be seared into the minds of her spectators so thoroughly that they wouldn't be able to keep from thinking of her amazing rack whenever their minds weren't otherwise occupied with their life. Contemplating her effect on other ponies made her cum again, and her mind briefly ground to a halt before she could achieve much other than shuffling vaguely sideways. At least her boobs didn't resist her much, all that milk escaping from underneath her bulk apparently reducing drag.

She couldn't recall the last time she had felt so incredible. She'd made a spectacle of herself in public before, but always in Ponyville and never with as much cooperation from Berry as today. Clearly, making it a shared activity improved the game immensely. Derpy had to take a moment to simply rest against her rack, enjoying its warmth, feeling her glands pulse and throb, clearly eager to continue spilling more milk than even her currently enlarged breasts could conceivably have held. She felt them grow engorged once again, posing a tantalizing question: Could she spray milk with enough force to shift the massive weight of her tits off her nipples? Perhaps once she attained her current size through regular growth, which always included her nipples – they weren't currently larger than they had been at the start of the day, so the upper limit of her output hadn't increased, although she hadn't reached it yet.

"Lemme try something," Berry muttered before stepping around her. "Legs out," she barked a command. Derpy complied, eager to see what the other mare wanted to contribute.

Berry grabbed Derpy by the shins and lifted her up, adjusting her orientation so her head faced the edge of the platform. The train was only just leaving. Derpy briefly felt somewhat ridiculous, being pushed closer to the edge like a wheelbarrow, her tits slick and slippery from milk, but noticing her own bow wave in the mess she'd made forced her to add another screaming orgasm to her tally. She couldn't get enough of the ridiculous excesses of her body, or how her sheer size altered the way she and others had to handle it.

Derpy badly wanted to tell the remaining onlookers that this wasn't some medical emergency she had to endure,  she wanted to grow until she crushed the station building, to produce enough milk to flood the track bed from here to the foot of the mountain.

"Well, uh, she seems to be enjoying herself," someone commented.

"Yeah," Berry agreed as she helped Derpy into a sitting position, breasts overflowing her lap so her milk could spray straight off the platform. "Kind of a problem, actually. It feels good, obviously, but, uh, getting hot under the collar risks stirring up her production, which keeps feeling good ..." Berry trailed off for effect. "Yeah, we're in public, but she's got to stay on top of both if she doesn't want to fall into an uncontrolled growth cascade. Then we'd really be here all day," she concluded, making an admirable effort to sound like that was a problem she had experience with.

There was a kernel of truth to the explanation, Derpy supposed, but considering how pleasurable it was for her to milk herself in front of an audience, she easily had both her lactation and her lust covered, two birds with one stone, really. She strained, briefly, to look at the ponies around her without going back to flooding the platform. The look of almost horrified fascination some of them sported stirred Derpy's body into a frenzy. Her immense tits gurgled and groaned, milk churning within, and another growth spurt made them inch closer to the edge. "Hah ..aah! D-don't give them ideas!"

"No!" Berry sounded appropriately panicked as she stepped up behind Derpy. She felt her partner grasp her shoulders and pull her back into a supine position. As Derpy would have predicted, she was immediately trapped under the weight of her own fat knockers. That she could still draw breath easily just reinforced her belief that she was made to have gigantic tits.

Her milk hit the roof above the platform, normally meant to keep rain off waiting travelers, with the force of two fire hoses. Derpy thought she heard some dismayed exclamations, but really, anyone who'd stuck around for the whole theater up to this point only had themselves to blame for getting a bit wet. Berry, grinning down at her, obviously felt the same.

"Guess getting you under control is a two-pony job today," the earth pony commented as she positioned herself by Derpy's head and reached down to grab her nipples. Not only was the feeling of Berry establishing a firm grip and pulling up quite delightful, it also allowed Derpy to reach down and stick her hands past her soaked skirt's waistband and start masturbating enthusiastically, fingers in her wet slit and thumb working her clit.

Berry lowered herself into a squat, apparently experimenting to see what the best stance for the current situation was. Still, she gamely kept milking Derpy, at least making the attempt to aim towards the tracks instead of straight up or to the sides, depending on how Derpy's boobs would come to rest when unattended.

"Hff..." Derpy shuddered. Maintaining coherent thoughts while so overloaded with sensation made her feel accomplished. "Would love to have ... have this as a painting. Over our bed."

"What? You soaked top to bottom in your own milk, bringin' yourself off furiously while I'm struggling to milk these jugs down to their usual size?" Berry sounded amused. "Maybe when all three of the girls are old enough we could risk hanging up something like that."

At last, both Derpy's libido and her breasts were coming back under control. A few concluding climaxes while Berry kept milking her a little longer than necessary to get her back to her regular size, and Derpy felt a bone-deep contentment. The embers of her lust were still and would always be glowing, ready to heat up again at a moment's notice. Her great glands throbbed slowly, languidly, reminding Derpy that she would always produce milk and would always feel full, but her breasts were pacified for now, no longer demanding to spill gallons of her thick cream just to show that there was no end to her bounty. The fullness she felt now wasn't desperate engorgement but the reassurance that she could have kept going for hours or days if she had wanted to.

Slowly, Derpy got up. "You're so good to me." Seeing Berry act like something of a put-upon caretaker had enhanced the experience, they'd have to revisit that idea in the future.

"Heh." Berry shrugged, suddenly bashful. "I had fun too ... anyway, y'think there's an employee restroom we could use? You lookin' like someone tried to drown you at a dairy farm might get us an in." She hadn't stayed wholly dry either, but her backpack had proven to keep its contents secure in the past, so at least they had a change of clothes.

Berry might have gotten away with letting the sun dry whatever had splashed her, but Derpy was absolutely soaked, including her hair. "We'd best look for someone to ask, then."  

Derpy had expected to have a good day, but learning that her boobs would grow if Berry asked it of her, and then Berry playing along with Derpy's public spectacle had left her giddy with excitement for the future.
> With a View
> --------------------------------------------------------------------------

Berry Punch was having a great day, and not just because they'd managed to freak out a bunch of strangers. She knew pretty well what Derpy looked like when she was overcome with lust and/or cumming her brains out, so she'd immediately noted the gratitude and delight the pegasus had felt for Berry playing along.

Frankly, the fact that the world's randiest pony was in love with her, of all people, had always seemed like proof to Berry that the universe was ultimately random. Although, according to Derpy, she'd been nursing a crush on Berry since before her boobs and her libido started growing.

Of course, she'd correctly predicted that Derpy would rely on her in Canterlot. They'd been holding hands since they left the station behind, because it had at least some grounding effect on the other mare. There were a lot more people in the streets than in sleepy Ponyville, and they'd barely been out of the train station before Derpy was obviously getting fired up again, although not yet to the degree that a stranger would recognize the signs.

Derpy had her free left arm crossed across her stomach so she could idly fondle the bottom of her right boob in a slightly less obvious manner than if she'd just reached up and played with herself. She'd never tried very hard to lose the habit of absentmindedly touching her own boobs, so getting used to doing it with a little bit more subtlety had been a success.

While Derpy tended to point to the fact that she didn't strain to carry her huge knockers around as proof that she was meant to have them, Berry was more impressed by how well Derpy tended to function in her daily life despite her insistent libido. Berry didn't have the pegasus' boob insights, but in her experience, Derpy's tits wouldn't run off the rails overproducing for most of the day, unless the mare specifically started fantasizing about it, and Derpy generally had enough focus for that.

Still, Berry did have a likely spot for a break in mind, just so Derpy could blow off some steam before the palace tour, so staying calm and respectful the whole way through was at least theoretically on the table. Although if people at the palace looked too obviously scandalized to see Derpy jiggle and wobble along, she might just decide to make a real scene, give them something to be shocked about.

"So," Berry picked a harmless topic. "I figure since Pinchy is still obsessed with trains, we could look into model train sets. Uh, the nicer, hobby stuff." She assumed her daughter would have already asked about that sort of thing if Ponyville's toy store were a little less provincial.

Derpy smiled at her. She was slightly flushed and her desire was obvious, if currently unimportant. "Aren't they a bit young for that? I saw a real nice set-up in a display window in Manehattan once."

Berry shrugged. "Well, the tracks and trains bit seems simple enough. The girls got steady hands and might like a bit of responsibility for fragile stuff. We shouldn't compare to professionally done setups, yeah?

"Right," Derpy allowed, but she still looked somewhat dubious.  

"Besides, maybe I ought to pick up a hobby anyway," Berry explained. "Something I can do with the kids."

"Hmm, sounds good." Derpy could relax perfectly well by gazing into her own cleavage and spacing out, so she probably hadn't considered a hobby for herself, although she was always in favor of shared activities. "Space might be an issue."

"True. I've actually been thinking of making the attic livable,"  Berry remarked. She was a quick study when it came to working with her hands and liked taking care of their modest house.

The set of stairs to the attic was steep and narrow, Berry thought that very soon Derpy would struggle to fit, but since she could fly, they might just knock a wide enough entrance into one of the gables in an emergency, maybe a little balcony. Of course, explaining that sort of workaround would just get Derpy more worked up. The pegasus loved the idea of having the world adjusted around her.

"We could put in a small bathroom, I think Sparks would love to have her own little apartment if she wants to stay with us," Berry continued to throw out ideas. "We could use her old room as some kind of hobby or play room, that seems like a better idea than just having a guest room or something."

"You just don't like visitors," Derpy accused, sounding amused.

"We got a perfectly fine couch if someone wants to crash. Lyra and Bons' place is barely smaller and they got no kids." Berry didn't think Ponyville was short on hospitality, so her own dislike of hosting people overnight seemed well compensated for. "Anyway, I just want the girls to have the option of pursuing stuff that interests them at home."

Derpy nodded, squeezing Berry's hand briefly. "I get it."

They spent some more time in conversation like this as they moved through Canterlot, getting some hayburgers for lunch. Avoiding dairy products in their food was a sensible precaution, even if Derpy didn't always get herself riled up with fantasies of dominating the dairy industry all by herself.  

At one point, Berry successfully distracted her partner from noticing an inactive fountain with an empty basin. That sort of sight tended to really get Derpy going. Berry didn't begrudge her that, but there was a schedule to keep and she had her own idea.  

"I'd like some shirts with text on them," Derpy stated without prompting.

"Yeah, like what? 'Unlimited Refills'?"

"Mhmm." Derpy hummed pleasantly. "Good idea. I was thinking 'They'll never be this small again'. I kinda missed being able to say that, earlier." She fondly patted the side of her rack.

Berry knew that it was one of Derpy's favorites to tell others or herself  'they've never been this big, but they'll never be this small again'. Berry chuckled. "Might start to sound threatening, the size you're at." She suspected many townspeople back home still told themselves that surely, Derpy would stop growing now. Berry liked to think that Derpy's size would be whatever her conscience allowed. It was fairly evident by now that biological limits didn't mean much.

Derpy just smiled before changing the topic again. "What'd you plan next?"

"One of the observation decks," Berry replied. Since Canterlot was built fairly precariously into a steep mountainside, there were no shortage of locations where residents and tourists alike could enjoy a view of the countryside below. "Got it on good authority that it's one of the less busy ones."

"I rarely bother to fly high enough for this kind of view," Derpy noted. "You'll like it, I think."

"Even if the view was an old hat to you, I was planning to make it worth your while," Berry stated with a grin.

"You're always full of good ideas," Derpy purred before putting a bit of a skip into her walk to make her breasts wobble more.

"I try," Berry nodded. "You might have mentioned something like that before, but I think we really should start hanging up mirrors. Big ones on the walls, small ones up in the corners, might help you maneuver around the house in the future."

Derpy giggled. "If I get too used to that kind of aid, I'll just keep bumping into other ponies or things when I'm out of the house."  

"How awful." Berry knew full well that Derpy would get a thrill out of that every time. "Well, I figure you can afford to go bigger. Sparkler's gonna stick around for a few years yet and the other two are getting old enough to get them more involved with the chores." The opportunity costs of having absurdly large breasts were something they didn't much talk about, because Berry wouldn't really mind Derpy being less able to help around the house over time, and it wouldn't make the pegasus worse at the emotional work of being a mother, which was the important bit since the girls were no longer helpless.

"If you're sure." Derpy managed to avoid sounding too eager. She always wanted to be larger. Berry had proposed some real absurd sizes, and while Derpy was obviously aware that such things weren't likely because she had neither the time to pursue them nor the will to occupy large areas with mountains of boob where it would cause problems for other ponies, she never had a gut reaction that said 'too big' or even 'big enough'.

"Sure I'm sure." Berry looked around. There were always ponies staring at Derpy. "Canterlot folk are awfully polite. Figured by now someone would have come up to hit on you."

Berry wasn't 'tall for a mare', she was just tall, and while she wasn't as naturally gifted as some earth ponies, she had a broad frame and worked out to keep her strength up. It wouldn't surprise her if most of these locals took a look at her and developed an urgent need to not get in her way. If it wasn't for Derpy's huge tits, Berry would be the memorable one of the two. She'd never cared about being conventionally attractive, that sort of thing hadn't had much survival value when she'd been growing up. That she was apparently Derpy's type had just been fortunate coincidence.

Derpy rolled her eyes. "In public, in the middle of the day?"

Perhaps neither Derpy nor Berry were particularly well informed about courtship behavior. They hadn't exactly had any sort of storybook romance themselves – they'd been friends for years and moved together for practical reasons before Derpy had mentioned her crush. They'd grown comfortable together.  

"Maybe not," Berry allowed. "Listen, I know you love pretending like your jugs are takin' advantage of you, but maybe you'd enjoy running roughshod over some meek sop. Plenty of ponies would call you 'mom' before drinking if it meant they get their hands on the greatest tits in the world for a few minutes."

Derpy blushed. "Well ... maybe. Sometimes I think it would be nice to hear people talk about them in that tone they use for the Princess." According to Derpy, Cloudsdale had a downright annoying quantity of statues, or cloud sculptures really, depicting Celestia. The mail mare had never been particularly worshipful.

"They're Derpy's boobs!" Berry tried to affect a tone of breathless awe.

"Y-yeah. Like that." Derpy bit her lip before smiling at Berry with barely restrained joy.

It was a good way to be looked at.

Berry changed the topic as they approached the observation deck. "Anything else you'd like, next time you feed someone?"

"I could ask you the same," Derpy replied. Her milk had changed some ponies, bigger boobs being most common.  

Berry shrugged. It wasn't the first time it had come up. "I'm not unhappy with my looks. Besides, why would I want to change, given the way you always look at me? Clearly I'm perfect for you." She had a bit more padding than strictly necessary, made her look slightly less fit than she was. Berry couldn't tolerate being hungry and probably ate a little too much even for someone who worked out heavily.

Derpy blushed some more and nodded. "I wouldn't mind wider hips." She shrugged. "I mean, I'm fairly close to ideal in that regard, and I wouldn't want my ass to get stuck in a door frame, but a bit more 'round the back would feel nice, don't you think?"

"Well, I hadn't thought about it before, but you're not wrong," Berry agreed. Derpy didn't look nearly as slender as she had when they first met. She'd put on muscle to support her growing boobs and her hips, thighs and rear had slowly grown as well. Berry had some difficulty guessing what Derpy would consider her ideal shape, since the pegasus' standards were so distorted by her huge tits. Sure, not getting stuck in doors was a clear statement, but while Derpy certainly had motherly hips, she was pretty far off from that, and it remained to be seen how close to it she would want to be. "Well, try to keep it in mind the next time you really grow. Obviously your body is pretty obliging," Berry reasoned.

"I'll try," Derpy agreed, although without the certainty she always had regarding her breasts.

"Great. And if it's any consolation, I do hope for good health and long life whenever I have a drink from you." Berry grinned. "Just in case you turn out to be some immortal Princess of Tits, I wanna be along for the ride."

Derpy nodded. "Good." She started rubbing a hand along the underside of one of her jugs, smiling proudly.

Eventually they reached the observation deck, which wasn't empty but not particularly crowded. The railings were fairly tall and topped by an inclined band of metal embossed with a relief of the landscape below, including names of visible towns and terrain features. Berry maneuvered Derpy to the railing and made a show of 'helping' her rest her rack on top of it.

"The view really is nice," Derpy commented. She grasped the sides of her breasts to adjust their position slightly. "You're always so thoughtful, Berry," she sighed, always enjoying being touched. The way Derpy talked about her sensitivity, the parts of the relief her boobs covered were probably clear as a picture in her head.

Berry stood behind the shorter mare and wrapped one arm around Derpy's midsection. "Yeah." She smirked. "You wanna be visible from up here eventually? Pair of hills in the landscape, hm?"

Derpy nodded lazily. "Sure," she paused a moment. "Nice ... intermediate size to maintain. Just long enough for everyone to convince themselves I'm done."

"Hm. Might not happen. They'll probably form a whole department just for watching you, and for figuring out what all that milk does to the countryside." Berry liked to think she'd gotten pretty good at painting scenarios which would excite Derpy. Attempts at quantifying or even controlling her seemed to strike a particular chord with her.

"Go on, please."

"Well, maybe someone would let slip how your milk's been getting into the groundwater and the soil, indirectly helping to feed ponies. That'd light a spark in your head, get you growing enough to set off the alarms."

Derpy sighed pleasantly as she crossed her arms atop her rack and leaned on it, probably just to do something no observer could copy, since it didn't look that comfortable.

Obviously there was a mental component to Derpy's growth, so far she had to at least see someone drink her milk for her boobs to react, otherwise she would have grown quite a bit in the days after first donating her milk to the hospital. Not that either of them were concerned with these details when it came to fantasies.  

"Anyway," Berry spoke quietly. "I've heard there's a decent chance to see the Princess herself on these tours. I figured you'd like knowing that someone like that knows who's got the biggest jugs in the world."

"Oh yeah," Derpy nodded eagerly. "Bet she's never seen anything like mine before." She spoke with conviction, despite the fact that an immortal like the Princess must have seen a great many weird things.

"I don't know," Berry trailed off, pretending to be doubtful. "Maybe she's not gonna react at all. Y'know, 'huh, these are big but I've seen bigger and milkier.'"

Derpy reacted with a sharp intake of breath. "I'm ... hff. Not a fan of the idea." She squirmed a little against Berry.

Berry reached forward and brushed a hand over one of Derpy's nipples. As she'd expected, they were rock hard, tenting the mare's shirt prominently. To her credit, Derpy wasn't leaking yet. Berry looked forward to what might happen later, now that she'd planted the idea that the Princess might see and be unimpressed by Derpy's rack.

"Don't want her to overreact the other way, do we?" Berry teased. "Put you in a lab, try to figure you out?" It seemed reasonable to expect that eventually someone would want to figure out how a pony who wasn't even a unicorn could create so much from apparently nothing.

Derpy hummed before saying, "I can't be contained." She sounded certain, but followed up the statement with a 'huh' as though the thought had been unexpected. Some boob feeling, probably.

"That sounded less threatening when you were talking about bras." Berry knew that Derpy didn't favor destructive fantasies, even when imagining totally absurd sizes. Derpy didn't dream about smothering entire cities, but she enjoyed the idea of being so vast that ponies settled on top of her mountainous tits. Still, clearly they'd have to further explore ideas involving constraints imposed by others. "Should I put together some kinda mock door frame for you to get stuck in?"

"You read my mind," Derpy praised, arousal clear in her voice. "I really felt like ... like I could have just burst out of those doors earlier." She reached forward to start pulling up her shirt over her nipples. "Gonna need ... I'll need release before the tour."

"Glad you decided not to cause property damage, then." Berry chuckled, using her right hand to  tweak one of Derpy's nipples, while she snuck down her left to the base of Derpy's left tit. "Bursting out of physical restraints is probably gonna turn out to be amateur stuff."

Derpy had always been able to expand to some degree simply by getting her jugs riled up and eager to spray milk, then denying herself for a while. The growth on Berry's demand on the train had been something new, and she was eager to see how her lover's boob powers and her control developed.

"I think you could go more abstract," Berry continued. "Maybe you could grow out of some situation you just feel stifled in. Formal dinner or some other fancy occasion, maybe." It wasn't one of her best examples, really, because Derpy enjoyed being inappropriately large for the current location or situation, but also because she was selective about when and where she'd cause a scene. Spicing up something mundane like a train ride was different from making a mess at an event other ponies might consider a rare treat to be at.

"Heh. What ... what if I felt limited by linear time?" Derpy started releasing thin arcs of her milk. They'd probably be scattered into individual drops by wind before landing anywhere. "You'd tell me if you remembered me bein' h-huge already when we first met?"

"Not bad," Berry noted her approval. Derpy used to rely heavily on Berry to come up with outlandish fantasies to get her hot, but nowadays she readily came up with her own ideas. Berry rewarded the other mare with a tug on her right nipple while digging her fingers into the underside of her left tit, right by the base. After years of exploring Derpy's body, that combination was the best way to get the pegasus to climax quickly and repeatedly which Berry had discovered so far.

Derpy bit back her moans as her milk sprayed off the viewing platform. Actual milking motions weren't necessary, really. The pegasus' body barely needed permission to let down milk, let alone any active encouragement.

"You could do all sorts of crazy stuff with time travel, but most of it seems ... too sneaky?" Berry gave Derpy's nipple a teasing pinch, causing a brief increase in milk flow. Her boobs reacted even to such a small, implied attempt to control them. She felt Derpy shudder in pleasure. "We'll have to collect some ideas."

"S-sure." Derpy stifled another moan, but collected herself reasonably quickly. It was just routine maintenance, after all.

To Berry, having to masturbate and milk herself several times a day seemed like it would be a huge hassle, but she was good at not caring about things that didn't directly affect her, and it was pretty fun to send Derpy spiraling from 'randy but functional' to overwhelmingly aroused with words or well-practiced touches. And even years after her boobs had started growing, Derpy still acted smug like she was getting one over everyone else whenever she had to cum or express a bit of milk during the day.

She doubted other ponies would continue to be as kind and thoughtful as Derpy with that kind of body. Or maintain the restraint necessary to make their little trip a special treat instead of just a day in the life.

"You good to go, then?"

"Hm." Derpy nodded. Toweling off her tits a little to avoid getting her shirt any wetter was just another part of the routine – for those special occasions were it seemed sensible. After all, Derpy was clearly immune to any discomfort wearing a wet shirt might cause, and liked to parade around reminders of her productivity.

"You gonna keep it together at the palace?" Berry assumed she would if everything went off in an ordinary fashion. If they didn't actually get to catch sight of the Princess, Derpy might not want to ruin the guided tour for other ponies.

"We'll see!" Derpy smirked as she turned, smugly checking for anyone who might have watched their little milking session. She started moving, striding really, head held high, back straight and tits thrust out.
> Better Than Planned
> --------------------------------------------------------------------------

"This is pretty much your fault, Berry." Derpy stood in front of a bathroom sink with her shirt rolled up. Long practice allowed her to let her milk flow freely enough that it arced into the sink with some force without overwhelming the drain. Unfamiliar observers would probably assume her letdown was out of her control, since she wasn't even milking herself.  

She'd considered making more of a mess but eventually decided against it. Really, Derpy had been exceptionally restrained.

The palace tour hadn't been especially exciting. Interesting, sure, and the architecture was nice to look at, if a bit ostentatious, but it was the sort of 'cultural value' excursion that would probably have bored Ruby Pinch and Dinky. They could always go again as a family should the girls express an interest later.  

Derpy would have taken the tour anyway, mostly out of a sense of curiosity, but apparently her boobs felt some special significance in wandering around the home of a powerful pony most of the nation held in awe. There'd been an oddly tense sense of anticipation, even though her rack had been generally well behaved.  

Her imagination, however, had continuously supplied her with mental images of flooding the pristine halls, or growing until her titanic tits burst out of the palace and took its place, supplying milk to the city and the lowlands around the mountain.

It was fun in a transgressive sort of way to imagine burying Celestia's palace under her tits, but since Derpy didn't want to do actual harm, she should probably leave government buildings intact.  

"I'm a terrible enabler," Berry agreed. "Kept it pretty subtle, though, didn't you?"

Derpy wasn't convinced that the Princess saying hello to their group of tourists had been some kind of spontaneous coincidence. Either way, she hadn't wanted to make the moment all about herself. "How often does a pony have a chance to meet Princess Celestia?"

She'd only unleashed enough milk to soak her shirt and leave her bounty dripping copiously off its hem before Berry had firmly requested they be shown to the nearest bathroom.

It made her feel good to control her limitless abundance so precisely, strong and accomplished even when she was worked up more than normal. Of course, cutting loose back at the station had also made her feel powerful.  

Occasionally, Derpy liked to imagine what it might be like to grow into a body like hers within hours rather than years, with no chance to acclimatize. To be rendered barely functional by her normal levels of arousal, to be completely helpless before the needs of her amazing breasts.

"Fair enough," Berry nodded. She was leaning against the tiled wall, playing with a coin, letting it wander across her knuckles. Berry had nimble fingers and enjoyed making Derpy think about feeling those fingers on her boobs without saying anything.

Derpy shook her head, then turned her attention back to the mirror so she could gaze into her own cleavage and watch her milk flow. Dreaming about being at the mercy of her constant lust was well and good, but the things Berry could do to her would probably completely fry her brain in that situation, and the other mare had made too much of an effort to learn her way around Derpy's body. She didn't want to be so mindless with pleasure that she couldn't at least appreciate the craft on some level.  

More importantly, that sort of thing probably would diminish the emotional component of their lovemaking, which was completely unacceptable. Making Derpy climax was trivially easy, anyone could do it. A lot of things and thoughts as well. She'd never want her mind to be so clouded that she couldn't recognize Berry's hands on her.

"So what now?" Berry sounded amused. "Just gonna stare at your own tits and see how long it takes for someone to check on us?"

Derpy nodded, humming an agreement. She could spend any amount of time contemplating her breasts, time passed quickly that way. It was soothing to just let her milk flow for no real reason. The way it completely failed to make her feel any less full was, as always, deeply reassuring. It was lovely to just take the time to enjoy her keen awareness of her breasts. Their beautiful shape, their weight, how full they felt, and, more abstractly, their eagerness to please, their immense potential for more.   

She closed her eyes, allowing herself to sink deeper into the wealth of sensation her breasts provided. Things she unthinkingly tuned out as she went about her life were easily noticed as soon as she stopped to feel and listen. The steady beat of her own heart. The thrum and throb of her production. The slow, ever-present tide of pleasure, always spreading from her nipples, through her bosom to her core, perhaps the reason why her lust could never be fully extinguished. Her milk, flowing through tight, wet passages. A world of experiences for her alone, as unique as her breasts themselves.

Just as her body was strong enough to bear huge breasts, so was her mind adapted to make their extraordinary sensitivity fascinating and rewarding instead of debilitating.

Derpy felt the air in the room change as Berry began to move. Although ordinarily an aspect of pegasus magic, she relied less on her feathers, feeling the shift in air currents most keenly as it brushed across her fur and the exposed skin of her dark, pebbly areola and nipples.  

Minute tremors jiggled Derpy's breasts almost imperceptibly as Berry crossed the room with a few quick strides to arrive behind the pegasus. She hoped that her sensitivity would continue to grow as her breasts did. It would be amazing to relax at home and feel her family moving around the house.

"Question," Berry spoke from behind her, wrapping her arms around Derpy's stomach. "If I can make wishes now, how'd you like it best? A request like earlier today, or maybe givin' permission?"

"Oh, I can give myself permission just fine," Derpy responded after thinking for a moment. "Requests, sure. Try giving orders ... might be nice to share the burden of command." She couldn't help but giggle, feeling ridiculous referring to any aspect of her breasts as a burden.

"I'll keep that in mind," Berry murmured before shifting her hands to rest on the sides of Derpy's boobs, gently rubbing them. The earth pony knew to apply a soft touch to avoid snapping Derpy out of her peaceful state of heightened breast awareness.

Derpy wasn't sure how long she'd stood there, simply enjoying Berry's presence, her own body, and the flow of her milk.

Eventually, the door to the bathroom opened from the outside. To Derpy's disappointment, nobody stepped in to gawk at her naked breasts. The voice of a mare addressed them.

"Once you are finished, the Princess would like to see you."

"We'll be out in a minute," Berry called back.

Derpy stopped the flow of her milk. As was often the case, the feeling of fullness was particularly intense for a moment, to remind Derpy that she'd never run empty. She sighed happily before making herself presentable. Without an audience, there was no need to draw out the process.

Berry grinned. "Alright, let's not disappoint the Princess."  

The pony waiting to direct them to the Princess looked like a stern sort with her glasses and dark brown hair done up in a bun. She didn't visibly react to seeing Derpy, but turned and strode ahead of them.

The earlier sense of anticipation returned with a vengeance, and Derpy's nipples were already stiff again. Her arousal was already growing, which was unusual. The soothing effect of spending a quiet, relaxing moment with Berry or their daughters normally lasted a little longer than that. Derpy supposed it made some sense, now that they were actually going to see the Princess, part of her clearly didn't just want to show off Equestria's best boobs, but also the fact she was exceptionally good at being horny.

After all, was there anyone else who would be so delighted that her desires were never satisfied, only lessened for a few hours? Who would be so proud to be literally insatiable? But Derpy was doubly proud, both of being built for endless sexual pleasure, and of having the will to be more than that, to maintain her job and her relationships, to enjoy other things in life.

Derpy felt her great glands throb with immense eagerness. She'd just spent however long spilling gallons of milk into a sink, and while that sort of things did appease her breasts reliably, they also often seemed even more responsive to her desires afterwards, as if they wanted to provide additional reassurance that their supply was inexhaustible.

The walk seemed long, and Derpy wasn't sure if that was some kind of power move or if the architecture just shook out that way. Although in fairness, each step of their brisk pace served to maintain the weighty jiggling of her barely restrained breasts, shocks of pleasure pulsing through them, so she probably wasn't keeping track of the distance too precisely.

She felt overwhelmingly productive. It wasn't something she could measure, of course, since the limiting factor of her output were her nipples, but no one looked at an erupting volcano and consoled themselves with the fact that it wasn't going to spew out all of the molten rock available at the world's core.

Of course, Derpy wasn't going to tell anyone outside her family that her breasts could feel full in a threatening way, because it would sound crazy. Sometimes she just needed to completely shatter any preconceptions about what a large set of tits might be capable of and wash the pieces out to sea in an apocalyptic flood of milk. She blamed Berry for raising the specter of the Princess being unimpressed with her.

Derpy wanted to leave the Princess with a lasting memory that would vividly jump to the forefront of her mind whenever she encountered fluids, round shapes and maybe the colors white, grey or blond. She was beginning to feel achingly tight, yet her breasts barely swelled. Preparing a surprise, she supposed.

She took hold of Berry's hand to help her remain centered when she realized that impressing the Princess probably wouldn't be as hard as it would be to surprise Berry. The taller mare had always seemed to take everything about Derpy in stride, being entertained by the way other ponies reacted to her fantastic body.  

If Derpy had regular boobs but was really into some obscure hobby, Berry would probably take an interest just to make it more comfortable to maintain their emotional connection and Derpy would probably still ask the taller mare to help her work out. The incredible tits were just an incidental factor of their relationship, although one Berry took full advantage of.

She bit down a moan. Berry taking advantage of her breasts was dangerous thinking right now.

Still, surely, surely meeting the Princess was such a special occasion that her tits could brew up something that would amaze and astound even her unflappable lover?

She missed a step and stumbled when her rack groaned and gurgled in response to the thought. She felt so heavy, a decade's worth of accumulated milk bearing down on her. Berry kept her from falling. Their guide's posture seemed to stiffen further, but she didn't say anything.

"Eager to meet her Highness?" Berry smiled knowingly.

"Y-yeah." Derpy nodded. It was becoming harder to focus, milk kept intruding on her thoughts. Why couldn't Berry just grab her tits and spray down that other pony?

Derpy took a deep breath and tried to focus beyond the urgent throbbing of her nipples and the heat at her core. Should she really be holding back her gift like that? Her boobs weren't really bound by biology, what if that endless vitality went for other outlets and infected nearby mares with fat, gushing tits? It might be better to erupt here and now rather than risk pushing something on other ponies they didn't want.

She shook her head. It had never worked like that. Her mind was just playing tricks on her. Berry didn't want bigger boobs and her body would never betray her by forcing them on the earth pony. Did she smell milk? Derpy reached for her nipples. She hadn't leaked. She could taste her sweet bounty on her tongue.

She had absolutely no idea how they finally arrived at a large room with vaulted ceiling and marble floor. There appeared to be no furniture but a huge bed in the middle and an absurd amount of throw pillows everywhere. A tea cart with snacks was parked by the door Derpy guessed they had just entered through. The bed might actually just be a big mattress on the ground, the sheets looked expensive so it still counted as classy. She didn't see any drains and couldn't stop a demented giggle.

"I think this is the orgy room," Berry commented drily. "No wonder it seemed off the beaten path."

Princess Celestia was very tall. Probably the tallest pony in Equestria. She was elegant and slender, despite being so tall, she was in proportion with herself. She was wearing a white dress which seemed extremely basic, although Derpy doubted it had been cheap. "It hasn't seen regular use for that purpose in a few generations now," the princess responded kindly. "More innocent minds know it as the pillow fight room."

"Good idea," Derpy conceded. There was a reason they had a large shower room in the basement, and it wasn't that Berry had her weight bench down there. It was simply the most practical place to have wild sex without the clean-up being too annoying. Sure, her boobs were always on their best behavior whenever they made love in their shared bed, but sometimes Derpy just needed Berry to absolutely wring her out, and they didn't have servants to clean up after them. She struggled to banish the memories of those times, so she didn't trust herself to explain any of that.

"Hm." The Princess crossed her arms under her modest bust. "Was it thrilling to play your games in my home, my little ponies?"

"Yeah," Derpy blurted out before Berry could come up with a cleverer response.

"I'm glad." The Princess surprised them with her answer. "I'm afraid these current generations of my little ponies are a little staid, at times." She shrugged, speaking fondly. "There are worse things to be, of course. Influencing prevailing attitudes isn't an exact science."

Derpy recognized the home stretch. As long as she kept it together just a little longer, she could make her move. She nodded numbly. Thinking of what was about to happen made it easy to smile.

"So we're here why?" Berry sounded only mildly curious. Derpy knew of course that this was the best case scenario, the whole trip had been planned for Derpy to get her kicks from showing off, but Berry would wait until they were home to be smug about how well it went.

The Princess nodded at Derpy. "I only know you from rumor and reputation, but I would like to hear about your gifts and, if you're agreeable, partake personally."

Derpy stood up straighter and thrust out her chest. "Of c-course." She smiled brightly, feeling like she was about to explode. "B-Berry, do the pitch." She swayed a little, willing her body to be patient.

"Heh, right. She permanently gets a little bigger any time she shares her milk with someone new. Some ponies get a little boost themselves. I guess her milk grants wishes. We've had nobody unhappy with it yet. Some ponies wanted something but got nothin', so maybe her jugs can magically tell if they had a bad reason for it?" Berry shrugged. "Also, Derpy gets incredibly horny thinking about her own tits. That's, uh, that's why she's drooling now."

Derpy nodded. She loved hearing these crazy things about her boobs voiced. She wiped her mouth, then crossed her arms under her boobs and lifted them. "Interested?"

Berry snapped her fingers. "Right, it doesn't do anything to kids except be really healthy. Really healthy. Ain't nobody and nothing her milk isn't good for. Should see our back yard, if our neighbors didn't know us, they'd think I was good with plants or something."  

"We had to cut down on having sex in the yard." Derpy giggled again. Their daughters had been very annoyed about all the yard work related chores. She was holding back a great tempest of milk, but at least the land would bloom in the aftermath.

"Have you considered that the magnitude of your bounty might be an indicator of your fertility?"

Derpy moaned. How many ponies could she feed? She could theoretically give milk uninterrupted for twenty-four hours every day. Having more children meant bigger breasts, larger nipples and more output. That way laid unchecked escalation. "F-fun idea, but no. I want to be g-good at raising  children, not just -hfff- feeding them. We're good with th-three." She rubbed her thighs together.

"Very well. Still, perhaps you should investigate the possibilities of surrogate motherhood?" The Princess strode over to the bed. Up close it really was too tall to just be a mattress, it was comfortable to sit on its edge for the alicorn. "I'm quite interested in your gifts. If you desire it, I would also be open to satisfying your needs before you leave." She nodded at Berry. "That goes for both of you."

If Berry wasn't okay with having a threesome with Princess Celestia, Derpy would accept it and leave. She'd probably explode somewhere between here and the train, but that would be fun as well. Still, if Celestia thought she was a match for Derpy's libido, Berry would probably just stick around to watch her fail.

The earth pony shrugged. "I'll try anything once." It was the exact thing she'd said whenever Derpy had some suggestion for spicing things up, as though getting an invitation from the Princess herself was just some new twist on having sex with Derpy.

"Alright!" Derpy tore off her shirt and worked herself out of her skirt and underwear. She approached the Princess. Celestia was tall even sitting down but unlike Derpy she could still hunch over quite a bit while seated.

She felt the Princess' lips on her thick nipple. "Watch this, Berry!"

Celestia only had a moment to frown in confusion before the tethers of Derpy's control snapped. Two thick streams of milk erupted from her nipples with tremendous force. The rush of milk stung, force enough to cause discomfort even though her breasts were tuned to provide only pleasure. Derpy climaxed immediately, but she was well past where once would be sufficient.

The Princess recoiled, gagging and coughing. She dropped backwards onto the bed to escape the milk which had already covered her face and drenched her hair. She started moaning, whatever she had swallowed enough to trigger whatever change was to come.

"Hah, damn." Berry sounded terribly amused. She hadn't gotten naked yet, but already had one hand down her pants to warm herself up. Derpy had long since accepted that the manual approach got the best results to get Berry going.

Derpy gasped as she felt her own change coming. Her own growth had always been quite brief, but the felt filled with terrible energy and the pulsing in her boobs told her that this was going to be a big one. She stumbled towards Berry and wrapped her in a hug so the other mare could feel her grow.

Despite years of experience, even Berry couldn't quite keep from flinching when hit with the full blast of Derpy's lactation. She grabbed and spread those twin geysers to stop them from hammering her body. Derpy hardly felt disappointed that she didn't have enough cleavage to engulf Berry's upper body, but something told her that was about to change.

New titflesh bubbled into existence obscenely as her boobs lurched bigger, blasting Derpy's mind with pleasure. Her whole body tingled. She grew more solid in some indefinable way as her body adjusted to more growth than she'd ever had at one time.

Derpy couldn't think, but she felt Berry's hands exploring her body as her hips stretched and grew wider. Her ass also grew fatter and rounder under her lover's hands, full and tight.

"Hm, could park a drink on your hips ... or your ass." Berry whispered, making Derpy squirm.

True to her nature, she was most enticed by the feeling of her breasts enveloping Berry. Their true girth was hard to judge in this position, but it was breathtaking to feel so much of the other pony with her tits alone. With her rack embracing Berry's body, Derpy hugged her and spread her wings to wrap around both of them. Had her wing span increased as well?

In that moment of privacy, she kissed her lover. "Thanks for planning this trip."

Berry smiled. "Gamble paid out better than I expected. Think you did a number on her, though."

With her own growth slowing, Derpy became aware of other moans in the room. She stepped back from Berry, nearly losing her footing as her tits slapped together, sloshing and wobbling. Despite forming a long, tight line of cleavage, each was about two feet across, and even near their base their girth was so great that the skin of her breasts appeared to extend sideways from her rib cage. They dominated her chest, sitting so heavily on her body that they appeared eager to ooze around her torso despite the fact that they clearly maintained an impossibly attractive shape in general.

She wasn't anywhere near big enough to just lay down on top of her tits and sink into their vast softness, but she felt as though she was getting a beautiful glimpse of that future. She was still gushing milk, but her nipples were now roughly the size of Berry's fists, so they no longer strained to withstand the volume of her previous output.  

Seeing Princess Celestia was enough to briefly shock Derpy out of her appreciation for her own body. The Princess had grown, Derpy guessed she had to be nearly ten feet tall. She'd burst out of her dress. Her body was not quite buried under a quartet of enormous, heaving tits.

Derpy was pleased to observe that any individual breast was still smaller than her own, and the Princess was not obviously lactating. The royal jugs seemed less firm than Derpy's, judging by the way they deformed as Celestia groped herself. In any case, having two pairs of breasts seemed like an interesting idea to Derpy, although she wouldn't currently be willing to double her current total mass, or divide what she had to make four.

Most surprising however was the enormous dick with which the Princess was titfucking herself as two balls the size of Derpy's head pulsed and churned between Celestia's legs. Her horn was blazing, two additional spectral cocks were thrusting into her horizontal cleavage from each side

"Huh." Berry had moved next to Derpy. "Must have been something subconscious," she declared. "If she'd planned this out she wouldn't be falling just short of sucking her own dick."

Derpy laughed. "Probably, yeah."

The Princess came with a long, sloppy moan, but neither the climax nor a face full of her own cum caused her to falter.

Taking a step forward, Derpy was only kept from falling to her knees by Berry's quick reaction. The  pleasure her breasts provided had always increased with their size, but she had never grown this much at once. Yet clearly there had been another change. Derpy stood and reached for her sex. "Touch me, Berry."

"Y'know, you were right," Berry idly commented as she stepped up behind Derpy and reached around to probe her wet snatch. "Getting as much tit as you got at once really does mess a pony up." She made a disapproving noise.

They stopped talking, tenderly exploring Derpy's folds. Her clit was engorged, although what fascinated her were how pronounced her pussy lips had become. Thick and pillowy, Derpy could already picture how amazing they would look with a pair of soaked panties clinging to them. She adjusted her stance, lifted one leg experimentally, and her outer lips were practically fighting for space.

Some other mare might have been concerned about getting aroused just from walking around as her pussy stimulated itself, but Derpy doubted she'd even notice the difference considering how amazing her tits felt once she was in motion. She was already overflowing with sexual energy all day every day. "Do you think you'll like that?" That question was of far greater importance.

Berry's fingers traced Derpy's nethers almost reverently for a while longer before she answered. "Yeah. Feels good. There's so much of you, s'just right if you're plush down there, too."

The Princess was still furiously masturbating.

Derpy huffed, taking a moment to reduce her milk output to a trickle. "I am looking forward to being re-introduced to your tongue, but this was going to be a threesome of some sort and I'm gonna have that dick." The idea seemed ludicrous, but she had a good boob feeling about it. Maybe all of her body was bigger on the inside. "Let's get her all the way onto the bed." The Princess had, after all, fallen back from sitting on the edge.

That did surprise Berry. "Really?" She moved to reposition the Princess, who barely reacted. She probably got a kick out of treating royalty like that. "If you can take that monster, I can stick my arm up your snatch to the shoulder."

"Ugh, it barely sounds hot when you put it like that." Derpy spread her wings and took flight, hovering above the bed. "You gotta help me aim."

The Princess only managed to complain incoherently as Berry liberated her huge rod from the royal cleavage and held it steady. "Man, we have to have a camera on hand when the girls are old enough to hear this story," the earth pony commented.

Derpy slowly lowered herself on the biggest dick she had ever seen. It initially felt like it split her open, but despite the resistance there was no pain. Was her whole body becoming as resilient as her breasts? She lowered herself gently, already bracing herself for a moment of pain, but it never came. She felt herself continuing to stretch around the intruder. She dug her hands under her breasts to place them on her stomach and she could feel it moving inside herself without causing harm.

Derpy laughed. "I really am made only for pleasure! This is amazing." She'd touched down now, straddling the Princess on her knees. She took a breath without difficulty even though she'd taken a cock longer than her arm all the way inside herself. There was also a chance that Celestia had always wished for a giant penis that wouldn't hurt normal sized ponies, but that was the more boring option.

Clearly the Princess also approved as she started bucking her hips.  

"N-next step!" Derpy was discovering a new way of feeling full. Not as great as what her boobs could provide, but variety was the spice of life and all that. She dug her hands into her tits. "Berry! You need somewhere to sit so I can eat you out! Give the order!"

Berry's face lit up with recognition. She was as well versed in Derpy's fantasies as Derpy herself. She knelt down next to Derpy and the Princess. Then she hesitated a moment, probably feeling silly. Finally she put her hands on Derpy's right tit. "Alright ladies, grow! And don't hold back on the milk. We want this to be a catastrophe."

Celestia climaxed at that moment. Hot cum flooded Derpy's insides as her breasts started to swell rapidly. She felt her stomach bulge with Celestia's load "Yes! More, Princess!" Derpy came and her milk started gushing again. "More!" She demanded it of the Princess and of her own body.

Derpy got her wish. Maybe the Princess had entered some kind of pleasure cascade, in any case she pumped load after load into the mailmare. Derpy felt herself swelling until she felt as gravid as she'd ever been shortly before Dinky's birth. There should have been some backwash by now, but at this point she could just as well assume that her body somehow turned all that extra cum into more productivity.  

It felt incredible to experience her breasts cover more and more of the Princess in front of her. Her tits once again felt full to bursting as they swelled bigger and rounder, spraying huge streams of milk across the room. Derpy stopped being able to keep track of the situation when Berry started experimenting how she was going to get into position. Being fucked by the Princess from below, her breasts being treated roughly by her lover, spraying milk all the while, it was finally enough to overwhelm Derpy momentarily as she climaxed again and again.

She couldn't have lost more than a few minutes. Derpy returned to her senses just in time for Berry to rest her thighs on her shoulders. The earth pony's body was wedged into her cleavage, perfectly position so that Derpy could put her tongue to work.

She took a shuddering breath. "I've dreamt of doing it this way for years." Berry had brought her more pleasure than normal ponies could withstand, so it thrilled Derpy every time she could get Berry off. Getting Derpy to cum was just daily maintenance, business as usual. Pleasuring Berry was special, and she set about exploring the earth pony's sex with her tongue.

"F-fuck, Derpy. You're good." Berry wasn't much for talk during sex.

Derpy lost any sense of time she may have had. She was being fucked by the Princess. Her tits were big enough to support Berry's weight. She was spraying milk, her breasts throbbing, the pleasure of Berry's weight alone supplying regular orgasms. The other mare still had the presence of mind to claw at Derpy's tits just as roughly as she liked it. From below, the felt Celestia's stiff nipples, her huge breasts dwarfed by Derpy's volcanoes.  Her thoughts dispersed. Only her pussy, her tits, and the work of her tongue had any meaning as repeated climaxes rocked her. The smell of milk was overpowering.

In fairness, Derpy did feel a little sore afterwards.

The three of them sat on an island in a sea of milk and ruined pillows. The milk level had never overtaken the bed, but clearly the mattress had soaked it up from the bottom. Princess Celestia gazed at the devastation. "We may have gotten a little carried away," the alicorn commented.

"I'm a little conflicted," Derpy mused. "It's fun to see how much chaos I can cause if I just cut loose, but we have good drains in our shower room for a reason. I don't have to stop until I feel like it."

"Our clothing is somewhere in this mess," Berry observed. "I put our wallets into plastic tubs from the kitchen this morning, those will be dry."

Princess Celestia turned to Derpy. "You can't mean that you're still not sated?" Somehow she was more surprised by this than by the fact that they'd spent so much time fucking that Derpy's careless lactation had flooded the room. The alicorn was clearly having to put in an effort to not be distracted by her new body.

Derpy shrugged. "I'm pretty sore," she allowed, knowing that the Princess probably wouldn't understand what a tremendous achievement it was to make Derpy experience even a slightly negative consequence for sex. "So I've had enough dick for ... a while. But otherwise? I could go on. If you wanted to." She fondled her boobs, back to the size she'd gotten after sharing her milk with the Princess.

Berry snorted, well used to the answer. "You literally can't fuck her until she stops being horny, you can only get her to a point where sex is a little lower down on the list of things she wants to get done. That's not on you. And so far no one has been crazy enough to want that for themselves."

"Well, the effect usually lasts a little longer," Derpy stated before sucking in a deep breath through her nose. "Surrounded by this? It's givin' me an itch that I didn't keep going until milk started flowing out the windows."

"Yeah, but please take some pictures and send us copies," Berry added, ably anticipating Derpy's wishes.

"I shall. Now, let us begin our recovery." In a golden flash, she teleported the three of them to a large, private bathroom.

Derpy winced. The bathtub was offensively large even considering the Princess had already been tall previously. There was no shower stall in sight.

Fortunately, Berry had no compunction about wading into the tub and grabbing the shower head above it to spray Derpy down. "You would not believe how bad Derps here is about bodies of water or, uh, containers full of things other than milk," she pre-empted the Princess' questions. "If we sat her down in this tub it'd only be a minute until she forgot why she shouldn't just start gushing until enough water and milk ran over that the tub's mostly milk." She shrugged. "Empty vessels are kinda alright and I can get away with spraying her down because I don't need to be taught how pathetic this is compared to what she could do. Besides, in the shower she can just leak without issue, yeah?"

"It's so amazing," Derpy couldn't help exclaiming. "Having you explain that stuff so matter of fact is really doing it for me, so maybe don't keep going."

"Heh, alright," Berry conceded. "You did real good today. Even caught me off guard."

Derpy couldn't help but preen, delighted by the other mare's approval.

"I suppose it's good fortune that you enjoy every aspect of your powers." Celestia looked at herself in a huge mirror. "This reminds me of a delightfully salacious story about myself I had the pleasure of reading about a century ago. I hadn't been aware of how much it stuck with me, to be embarrassingly honest!"

The Princess turned to face them. "I'm afraid you'll have to swear secrecy regarding these changes. I will have to disguise them and grow into them gradually over the next year or two." She smiled. "Perhaps we can repeat this once I've grown used to these changes and can apply a little more skill and a little less instinct to the encounter."

Derpy smiled, delighted. "Oh, that won't be a problem at all." 

After all, she still needed to sound out the Princess on what she might think about tits the size of mountains. Many potential problems would probably be easier to solve with such a powerful pony at least implicitly approving. Maybe she could set her mages and sages to look for a parallel dimension no one was using anymore!