The only chapter
The air outside was cold, white flakes of snow - each perfectly crafted by the talented pegasi that control the weather - fell to the ground and onto the white balcony railings of the extravagant Canterlot castle. Inside the room connected to the balcony were two ponies, snuggled together by the fireplace. The elder pony's chambers were lit with the cozy flames of the fireplace, which revealed many festive decorations on the walls, floor, and various areas of the Princess' room. Gold, silver, red and green tinsel hung from the ceilings as well as white strung lights. A tall tree decorated with beautiful ornaments and lights filled the rear corner of the room, illuminating the area it was in. Hoof crafted stockings hung above the fireplace - the same stockings Celestia and Luna had made together as fillies; the older sister's stocking was white and pink, while the younger's was blue and black with sparkles. The two aforementioned ponies lay together underneath a large, wool blanket, both looking at the fire and enjoying each others body warmth; as well as the warmth from the fire.
Celestia turned her head to the tree in the corner, gazing at the wrapped boxes underneath before turning back to her sister and smiling. "Luna, I know hearth's warming eve is tomorrow but... I want you to open your present now." the white pony bit her lip and used her magic to levitate a large, rectangular box. She set the gift down in front of the two of them, and waited for Luna to open it.
Luna smiled as her horn lit up, ripping away the wrapping paper and opening the box. Inside there was a smaller box, a set of red stockings with fluffy white trim, matching red and white trim panties, a red collar with a golden bell, and Sadie Saddles' Spellbook of Sexual Spells. The younger pony's cheeks flushed as she looked at each object in the box, and her curiosity only heightened as to what was in the little box after seeing the rest of the items. With a smirk on her face, she levitated the little white box, opening it and gasping when she saw a little red vibrator, looking over at her sister and smiling, eyes lidded seductively. She set it back down, and took out the stockings, standing up to slide them onto each leg. She then put on the underwear and collar, and laid back down next to her sister.
"Let's see what kind of spells this has... can't be anything I haven't seen before." She opened the book and looked at the table of contents. Each chapter was a different fetish, in alphabetical order. Luna flipped open to a random fetish and skimmed over the pages. It listed information on how to properly have fun with said fetish, any warnings to safety or health that may come with it, other various articles relating to the fetish, and at the end a list of fetish based spells and how to perform them. She turned back to the table of contents and looked down the list, looking for one that peaked her interest. As she neared the bottom, Watersports caught her eye, and she opened the book to the page number after the chapter heading.
On the front page of the new chapter was an illustration of a mare peeing. The dark-colored alicorn's blush deepened as her eyes scanned the detailed drawing, but she looked away to read about the newly found fetish. As each word registered into her brain, her arousal grew; she smiled as she read more and more about the fetish, her pussy moistening as she read all the different ways to explore watersports. Turning the pages as she read, she quickly got to the end as she had been eagerly reading, the words in the spellbook making her hornier than a mare in estrus. Luna read over all of the various spells, and closed her eyes as she cast one onto both of the ponies.
"Luna? What spell did you just cast?" Celestia inquired, though she didn't feel much different at the moment. She had been reading along with her sister, so she knew what Luna was reading about, but the younger of the two didn't say anything before lighting her horn up.
"Oh, this one right here, sister," Princess Luna pointed her stocking covered hoof to the third heading; Expanding Bladders: Advanced Spell Casting which was printed above a spell. She then looked back down at the page, and recited the fourth spell in her head, her horn lighting up as she cast it onto her sister; a devilish grin settled onto Luna's face as she watched Celestia's face change from relaxed to strained, the older pony's hooves suddenly flying between her legs as she held them against her vagina. The younger sister giggled and took the blanket off of the two of them, gently pushing Celestia onto her back, the two white hooves still firmly planted against the sopping wet snatch between her big, soft thighs.
Luna pushed Celestia's hooves away, making the white pony gasp as she clenched her pussy to keep herself from peeing. Luna spread her older sister's legs and got on top of her, their marehoods inches apart from each other; as their clits were about to touch, she cast the same spell she had just put on Celestia onto herself, her bladder immediately filling up. She gasped and lurched forward onto her sister's chest, their pussies smashing together as she doubled over from the sudden pinch against her entrance. The younger princess held back the wave of sloshing liquid inside her, pushing herself against the elder pony harder to keep the gallons of piss in of her bladder. As the pain went away and she was able to relax slightly without bursting, she started rocking her hips back and forth, rubbing the two love buttons together as the two mares held in their pee, enhancing the feelings in their clits. The fullness in their bladders increased their pleasure, sending shockwaves through their pussies as they ground them together.
"Ahhh... Buck... Faster," Tia moaned as she begged her little sister to scissor her, the darker pony happily obeying; the two ponies' moans increased as Luna fucked her sister with a steadily rising pace, thrusting her hips back and forth. Wet noises filled the room as the two mares' folds slid against each other, their entrances kissing as each sister tribbed against the other's soaking wet cunt. Luna grabbed onto her sister's shoulders and began to grind faster and harder than before, making Celestia moan louder; she couldn't hold it in much longer. "Lu-una.. I-I can't hold it anymore..."
"Let it out, Tia... I want you to piss all over for me," Luna blushed deeply as she talked dirty, feeling a little embarrassed as she uttered the inappropriate words.
Celestia let out a low moan as she relaxed, letting her bladder loose as her clit was scissored by her little sister's pussy. Luna's ears swiveled back to listen to the hiss as Tia peed all over the carpet, a heavy pattering noise filling the room as the urine hit the floor. Luna moaned and couldn't help but release her bladder as well, the two princesses peeing all over each other's pussies, asses, thighs, and the carpet as they thrusted their hips together. The streams hissed and sputtered as they squirted everywhere, the two vaginas they originated from passionately grinding against each other.
If somepony were to be standing behind the two alicorns, they would have seen quite the sight; two impossibly dripping wet mares scissoring each other while they both pissed all over - both ponies a moaning, horny mess as they fucked each other on the floor, covering the carpets in mare's arousal, piss, and soon - cum. They continued to rub their clits together, moaning into each other's mouths as they made out and gazed into the other's eyes.
Luna stopped grinding, and tightened her muscles to force her stream to stop. Celestia, however, continued to let herself pee all over the carpet, looking down as her stream arched and splattered onto the floor. Luna backed up, and sat down next to her sister, putting a hoof into the yellow stream squirting from her older sister's snatch. She pushed her hoof against her pee hole so she would stop pissing, even though she wanted her to continue.
The younger alicorn rose up and bit her lip as she walked over to Celestia's head. She looked down at her older sister and smiled, before positioning herself on top of Tia, then lowering herself; Luna began licking the pink, swollen lips between her sister's legs, in turn earning her a gasp. Soon after, the other mare did the same, both muzzles buried in each other's marehoods. The older, more experienced mare expertly swirled her tongue around the darker pink clit against it. Luna moaned into the sopping wet cunt she was sloppily licking at; she licked around her sister's clit as her moans vibrated against her, making Celestia squeal quietly. The darker mare grabbed her sister's huge, voluptuous, white ass cheeks, spreading them as she ate the lighter mare's pussy. Tia sucked her clit into her mouth, swirling her tongue quickly around Luna's love button; Luna's legs began to tremble as she felt the aching pressure in her bladder. She decided to release her bladder all over Celestia's face - not caring if she pissed into her sister's mouth. To her surprise, her sister backed her head up and opened her mouth, swallowing mouthfuls of her golden piss; Luna looked back and watched as she peed into the older mare's mouth, moaning as she saw Celestia swallow it. She turned back and continued to eat her sister's pussy, moaning against the twitching snatch. Her tongue lapped harder at Tia's clit as her stream became more powerful, hissing loudly as her urine sprayed all over the white mare's face. Her piss soaked into Celestia's fur and mane, the carpet, and all over her own stockings; the formerly bright red stockings and panties were now a dark red, stained and soaked with her royal piss.
As her stream died down, Luna started to passionately eat at her sister's clit, the built up tension approaching it's release. Luna lapped as fast as she could at the sensitive nub, sensing that Celestia was getting close. The thick white thighs closed around Luna's head, and seconds later she felt a strong vibration against her clit, hearing a buzzing noise as she was surprised by the sudden pleasure. Celestia used all her focus to hold the vibrator with her magic - she was about to cum and she wanted Luna to cum too. Both mares moaned loudly, surely loud enough to raise the guards' eyebrows (and dicks) on post outside their door. Screams filled the room as Tia neared the edge, holding on and waiting for her sister to cum with her. She turned up the setting and pressed the little red toy against Luna's love button harder. The younger pony gasped as she began to cum, her older sister relaxing her muscles and allowing herself to cum as well. Both mares screamed as they squirted, covering each other in sticky mare cum. Their bodies shook and their backs arched, their hips bucking as they both came in unison. The two sisters squealed as they rode out their orgasms, breathing heavily when they finally subsided.
The two sisters lay against each other, still in the 69 position as they relaxed and breathed, basking in the afterglow of their orgasms. They both smiled as they closed their eyes, sighing in pleasure. For minutes, only the sound of heavy, to gradually lighter breathing filled the room; Luna and Celestia nuzzled against each other's thighs, both of them placing light, loving kisses on the other's legs. After a few minuted of nuzzling and coming down, Luna stood up, removing the piss soaked clothes and reaching a hoof out to help her sister up. The two ponies lazily dried off with towels, and walked to the bed together, slipping under the covers and cuddling against each other. They both smiled as they slowly drifted off, the two of them intertwined with each other.