Marble Pie was fast asleep. Her conscious state was pinned down by a parasite in her head, forcing her to dose up on melatonin. But as the sun peaked in the sky, the parasite sending out tendrils in her head judged itself grown enough that it could control its host as it needed. It eased up the dose of melatonin, relaxed its tight grip on the girl's unconsciousness, and let her body flush the chemical away naturally.
Slowly, Marble's mind began to pull itself from two days worth of sleep—a little early. The last minutes of her long sleep were spent wrapped in a warm, naughty dream. She was moment from waking up, with one hand rubbing under her nightshirt, when Marble sensed someone in her bedroom.
"Who the hell are you?" Marble tried to scrub the crusty sleep from her eyes and recognize the intruder. They didn't have pink hair, nor the muted tones of the rest of her family. She reached to the side and found her alarm clock.
Rainbow Dash's reflexes kicked into high gear when a projectile flew past her head. "Hey! Marble! Calm down! Your sisters let me—" Faster than a snake could strike, Rainbow Dash caught the lamp as it flew toward her head. "Stop!"
Getting a good grip on her bedside chest of drawers, Marble started to lift it from the floor when two things filtered through to her adrenaline-soaked brain: her invader was actually Rainbow Dash, one of her sister's friends; the arousal of the last dream she had was stretching its way through her body.
"Okay, yeah. You know me, right? Please stop throwing breakable things at me." Backing toward the door, Rainbow Dash gestured to the little box she'd been carrying (before she grabbed the lamp). "Look, this is embarrassing as all heck, but you are really going to want what's in that box. They're clean, new, and have fresh batteries."
A burning fire started to flare up in Marble Pie's body. She had grabbed the covers of the bed and tried to cover herself with them, but another part of her wanted to stop Rainbow Dash from leaving. Her aching body wanted sex, the parasite in her head did what it could to encourage her. "R-Rainbow?"
"Yes. Rainbow Dash. Look, I know how it feels to deal with this. It gets easier." Something in Rainbow Dash tensed. There was an odd sensation in her head, a desire to do something. Shoving whatever was going on in her brain to one side (and unable to properly understand what was happening anyway), Rainbow Dash took another step toward the door.
Marble ached in all the right ways, but her mind picked up on Rainbow Dash's attempts to reach the door. "Please?" She reached a hand from the covers. Her paranoia about other people should have been blasting her into a corner, but her need was too strong. "I need… I need help."
Rainbow Dash bit her lip. She knew exactly what Marble Pie wanted help with. Her second instinct was to flee and leave her friend's sister to her fate, but Rainbow Dash's first instinct—always—was to help. "Spicy puts up with me despite his preferences. It's not like I need to get off after all."
Shaking her head to clear it of the odd words Rainbow Dash was saying, Marble crawled out from under her covers and across the big bed. "Please?"
"Stay there." Surprised a little at how much command was in her voice, Rainbow Dash walked the few steps back to the toys she'd left. "Have you masturbated before?"
Marble blinked at the command and question. Her heart raced, and in her head she struggled with her lifelong aversion to people. But Marble Pie's need was so strong she managed to fight against it for only a few breaths before she let out a whimper. "Y-Yes."
Rainbow Dash sighed in relief. She reached down and grabbed the small box and walked over to the bed. "Do you have something to keep your bed clean while you get off?"
Nodding, it took Marble Pie nearly two seconds to realize Rainbow would want her to get her towel. She leaned to the side of the bed and reached to the drawers under it. Pulling out a towel, she quickly spread it on the bed and climbed on.
When Rainbow Dash turned on the vibrator, however, all Marble's attention was on it. Eyes widening, Marble Pie stared at the buzzing device. "W-W-What's that?"
"This is your new best friend. He has a big brother, but you can meet him later." Passing the toy to Marble, Rainbow Dash smiled a little at Marble's eagerness. "Hold on, don't go charging the gate. Even this horny, you want to work up to it. Kiss him, lick him."
Eyes widening, Marble nodded and looked at the little, pink toy. It was a little longer than her middle finger and made of hard plastic. Following directions, she leaned to the toy and kissed it—then giggled.
"Yeah. I laughed myself silly at the thing. But you can trust me, he's great at scratching itches. Open your mouth—slowly—and feel how big he is. Close your eyes." Something about the situation shifted in Rainbow Dash's mind. This wasn't really sexual, she wasn't even touching Marble. She vowed to talk to Spicy about it later.
The humming toy slipped through Marble Pie's lips, causing them to tremble along with the tone it put out. She closed her eyes and did what Rainbow Dash told her.
Rainbow Dash couldn't help smiling at Marble's excitedness—somehow, a bond of kinship coiled tight around her and Marble. "Now work it around a bit. Feel what it's like when that buzzing tip touches the top of your mouth, the back of your throat."
Giggling and gasping, Marble rubbed the toy everywhere, even feeling it thrum against her teeth (although that wasn't as much fun as the other places). Finally, she curled the edges of her tongue up each side and let the buzzing tremors flow all the way down into her neck.
"That's it. He's nice, comforting, and he'll never let you down. Next, t-t-t—" Rainbow Dash bit back at her problems, telling herself she wasn't involved with a girl. "Take off your shirt. Are you wearing anything else?"
Marble shook her head, holding her new best friend in her mouth while she pulled the oversize shirt over her head. She looked at Rainbow Dash, waiting for instructions on what to do next. She'd never been this close to someone while doing something so intimate before, but it felt much better than getting off alone (not that a parasite stimulating her body had anything to do with that).
Dammit. I wish I could be more at ease with this, Rainbow Dash thought. "Okay, now you want to see what he can do for you in other places. Take him out of your mouth and settle him between your breasts." The slightest flicker of her old jealousy came back. Rainbow Dash knew she was the same age as Marble, yet there was a long way between an A cup and a small C. "Lay back, let him rest there, and put a hand to each breast and gently squeeze them in around him." She had never done this, but Rainbow Dash had spent a lot of time lately looking up masturbation guides.
Tilting her head back, Marble squeezed her breasts on each side of the toy, feeling the vibrations tremble through her sensitive breasts. She let loose with hungry little mewling whimpers and massaged her breasts around the vibrator.
Inside Rainbow Dash's head, her parasite, now merely an extension of her own self, carried out the desire she'd focused on. It weakened pathways that made her feel tense around other women, not a lot, but enough that she wasn't unconsciously clenching her fists anymore. Once that edge of panic was gone, the brain-altering addition to her head ceased its work.
"Pinch a nipple, your left one." Rainbow Dash's heart beat a little faster. She wasn't topping Marble, not how she understood it, but she needed guidance, and Rainbow was there to give it. "Again, tighter."
The voice kept telling Marble to do things that had her out of control. She squirmed her body, rubbed herself, and felt amazing. In her head, her parasite was very excited—so far as such a creature could feel excitement. It fed on the rush of sex hormones from her blood, and in return it triggered her brain to produce yet more. A feedback loop that ensured its host would not only feel good, but feel good about feeling good. It was also no small reason why Marble Pie was fixating on Rainbow Dash.
"When you think you're ready, slowly guide the tip of your new best friend down your chest, down to your belly," Rainbow said.
Despite Rainbow Dash's urging, Marble wasn't ready to comply. She shook her head, ground her thighs together, and in a moment of perfect bliss she reached her climax. "Ffffuck yes!" But it wasn't over. Marble wanted more, needed more. With thunder echoing through her muscles, and lightning crackling around her mind, she knew she was ready for what she'd been told. Slowly, she guided her toy from between her breasts and down to her belly.
The buzzing of the toy did nothing for Marble but fill her with anticipation. She tilted her head up, mouth panting, and looked Rainbow Dash in the eyes.
Rainbow Dash had that jolt of kinship, but while she still had no desire to actually participate with Marble's masturbation, there was a little less anxiety about being with another woman's presence. "Leave him there for now. Spread your legs a little and trace down with your right hand. You know what your target is."
Marble Pie nodded while her right hand began its journey. Her left held the buzzing toy at her navel, but the moment her fingers encountered her outer labia she started making soft, whines again.
"Hold still. You're tough, strong. Don't fight your muscles, let them hold you." Rainbow Dash watched as Marble's left hand began to bring the toy down. She smiled. "You've got the right idea, but don't push him in yet. Rest him along your slit, let him nuzzle and learn what you feel like."
The toy, it turned out, lit a white-hot fire within Marble. Her eyes flew open the moment the vibrations began to flow directly into her vulva. She tried to keep her legs steady, but kept giving little humps to the air. "N-Now?"
Rainbow Dash nodded. "Push him in. You've both earned this."
Marble's fingers trembled as she turned the toy so the tip aimed directly into her. She only barely touched the thing, teasing past her outer labia to the inner, when the biggest orgasm of her life (so far) struck. "Fuck! Fuck! Fuck!" she cried, and kept crying. Clenching her muscles, Marble pulled her knees up and her whole body trembled.
Loud knocking failed to get through to Marble Pie, but it did cause Rainbow Dash's ears to twitch and turn. Stepping past the trappings of a young woman's bedroom, Rainbow eased the door handle around and barely poked her head through the gap. Behind her, Marble grabbed up a pillow and tried to jam it into her mouth.
"Rainbow Dash? Uh, what's going on in there?" Sunset Shimmer was blushing red and doing her best to hold back Pinkie Pie. "We heard yelling…?"
"Everything's fine. Just relax." Rainbow Dash held up a hand in placation. "Marble woke up and she's fine. Just give me ten minutes to help her relax, and we'll be out. Okay?" She looked more significantly at Pinkie Pie than Sunset Shimmer, trying to reassure as much as she could.
Pinkie Pie felt anxious about her little (by minutes) sister. "If you say so. But if you don't present Marble in ten minutes, I'm coming in with an axe!"
Sitting on her bed, on the towel she normally used for such situations, Marble Pie was wrestling with a lot of feelings. She felt good, better than she knew she ought to. Turning her head, she watched Rainbow Dash close the door. She breathed a sigh of relief—then froze. By all rights she should be anxious and terrified still: there was someone in her bedroom while she was stark naked on the bed. More, Marble had just masturbated not only with the person present, but following their instructions.
"So…?" Rainbow Dash would normally have looked away, but she couldn't help but keep watching Marble. "You got sick with the same thing Rarity and me did. The good news is you get the best orgasms of your life. The bad news is you can't really avoid wanting them, and we don't know how to fix it."
Sitting there, with a vibrator buzzing a few inches from her groin, Marble Pie couldn't help but latch onto the problem. "It can't be the same thing. We haven't been in contact at all! What's the infection vector?"
"You're right. We have no clue what it could be. If you want to talk with someone who's getting all over this, you'll want Twilight." Rainbow Dash had to fight back a laugh at the situation. "But that can wait until after your sisters want to beat the door down. Do you need some help cleaning up?" The moment she asked, Rainbow realized it was a stupid question.
In Marble Pie's head the parasite kept working. Conditioning its host with reward chemicals for feeding it, while it built extensive new pathways in her sub arachnoid space.
"Do you have her number?" Being reminded she was naked and messy didn't distract Marble from the topic she was latched onto.
Rainbow Dash shook her head. "Not until you're mobile, outside, and your big sister isn't going to punch the snot out of me for—for whatever it was we just did." She made herself look at Marble. The gray-skinned girl had all the curves Rainbow Dash lacked, but she wore them well. Spread out on her bed naked, Marble Pie was giving quite the show. "Do you need anything else?"
At any moment Marble expected to have her need for solitude awaken again, but she felt too good for it to so much as tingle a warning. She looked up at Rainbow Dash and nodded. "Can you clear a path out there for me to get to the bathroom?"
"Left?" Rainbow Dash got a nod from Marble before continuing. "Yeah. Gimme about ten seconds. If I can't get them to move, I'll make them move." Turning for the door, power surged through Rainbow. A rush of sensation that reminded her that she and her friends seemed to be a little more pony all the time.
Marble watched Rainbow slip out, and started counting in her head. "This is so bizarre. I shouldn't feel this good. Ugh, forget it Marble. She's clearing the way, you need to be ready to move." Using the towel as best she could, Marble Pie cleaned herself up and climbed off her bed. Her legs were shaking a little, but she was quickly getting herself under control. She grabbed her bathrobe from its hook on her door and wrapped it around herself.