The Carousel Boutique was devoid of any customers, all having gotten what they needed in a timely fashion, or having made their orders for another day, before leaving the store. She put up the closed sign, to keep more from coming in. The place was cleaned and everything was in order. She had no pressing orders she could currently fill, still waiting on materials to be mailed so she could finish. She had no appointments she needed to make, giving her the rest of the day off. Absolutely nothing else required her attention, she could do as she pleased now. And by Celestia she wanted to please herself.

Doors locked, windows close, and blinds drawn shut, Rarity made her way to her bedroom, slipping inside and shutting the door. She began to undress as she sauntered towards the bed, her marecock twitching in excitement. She was a tall mare, at eight feet tall, towering over her friends. Her mane and tail where a gorgeous purple color, well cared for, and curled in a way that they spiraled towards the ground. She tugged her shirt over her head, tossing it onto her dresser, her skirt fluttered to the ground around her ankles, before she stepped out of them, and she unhooked her bra, releasing her massive canteloupe-sized breasts with a slight bounce. A light touch of her purple nipples sent a wave of pleasure through her, making her gasp lightly. Her panties found their way to her nose, a quick sniff of her own arousal spurring her cock on, before being thrown to the floor.

She laid down on her bed, face up, and stared lustfully at her cock. A beautiful, three foot long dick long but slender, a brilliant purple color, the same as her main and tail, throbbed in front of her, dribbling precum down her shaft. A pair of large testicles, each one twice the size of Applejack's prized apples and colored a deep dark purple, almost black, adorned the underside of it, growing ever so slightly as it created the load that was to come. Her breath shuddered as she reached for her rod, wrapping both hands around it, gasping at her own touch.

Oh she needed this. She'd gone a month so far without touching herself like this, with so much going on, constant orders and friendship emergencies. She was ready for this, so very ready for it, and she knew that there would be a mess to clean up after this. She began running her hands up and down her shaft, gliding gently over her flesh, gasping softly every time she hit the medial ring. She could feel the veins traveling all over it, plumped up with blood to keep the massive thing hard. She could smell her own musk as it filled the room, causing her cheeks to flush red as her arousal skyrocketed. She began moaning throatily, quiet at first, but growing louder as she went on.

She hastened her movements, causing her breasts to shake as she bounced her hands around. Her breathes were getting shorter and faster, and her marecock twitched and jolted slightly as she sped up, spurting out larger and larger loads of precum onto her belly. The amount of cum drooling out of her at this point would put entire ponies full loads to shame, but for her, it was almost nothing. Her balls were still growing, having already doubled in size, seed churning within them waiting for release. Her hands were a blur of movement, wet and sticky from pre, and she felt her orgasm coming fast.

She quickly pushed her cock down between her legs towards her bedroom door, in an effort to keep from making a bigger mess on herself and her bed, and gave a loud moan as cum traveled up her shaft. She heard a door open, and a "Rarity..?" call out when the head of her cock flared out, and cum blasted out. Rarity's eyes rolled into the back of her head, and her eyelids fluttered closed as she shot long, thick ropes of cum out of her cock, coating whoever had opened her door in her seed. Whoever was there gasped as it hit them, but didn't move out of the way, instead just staring at the cock before them. Rarity's balls pumped out more and more cum, bouncing and shrinking as they did. Finally, the cum slowed down, losing distance and no longer covering the uninvited guest, before going down to a drool that dribbled down the shaft. Her chest heaved as she reveled in the afterglow of her session. She'd need more, she wasn't satisfied yet, but she felt good.

"Uhm... Rarity?" She heard a voice from her doorway. Rarity quickly sat up to stare at whoever had come in. She saw her sister, Sweetie Belle standing there, covered in ropes of cum. Sweetie just stared at her sister with wide open eyes.

"I uh... came from Applebloom's. I just... started my first heat... Applejack sent me home, but mom and dad aren't in town today, so I... came here..." Her voice quivered as she spoke, her eyes never leaving her sisters cock, a look of need in her eyes. Other than the coat of cum, Sweetie Belle was naked, as per the usual. She never liked wearing clothes that much, even to big events and such, preferring to go in the buff, even in the winter. Her arousal at what she just saw was becoming apparent. A mares first heat marked their passage into adult hood, and triggered a lot of changes, very quickly, in mares. Where just yesterday she stood at four and a half feet, she was now at five, and slowly growing. Her once flat chest was filling out, once an A cup, now filling up quickly, already the size of apples. What was once a four inch dick and a pair of grape sized balls, where now inching down her leg, an eight inch cock and balls three inches across each, and was fully erect. The arousal was causing her to grow quickly, and Rarity saw her little sister developing into a woman before her eyes.

Rarity was still very horny, and her very naked sister was just standing in front of her, musk pouring off of her. Rarity wanted her, bad. She knew she shouldn't. She should apologize, clean her sister and her room, and help her sister get through this. But her mind was muddled right now. Arousal still flowing through her from a long lack of release. She stood up off the bed, and walked towards her sister, swaying her hips as she moved forward. Sweetie Belle still had her eyes locked on Rarity's dick, watching as it bounced back and forth with Rarity's walking, her own cock twitching and spurting out precum. Rarity put a hand on her sister's shoulder, and used the other to wipe cum off her face and chest.

"Oh Sweetie Belle! Just look at you! Your first day in heat and you're already growing into a mare! Here, come get on the bed, and I'll help you through this, darling," Rarity purred as she led Sweetie along. Sweetie, her mind filled with need, just nodded and walked along. Rarity laid Sweetie down on her bed, face up, and sat next to her. She ran her hand over Sweetie's growing breasts, feeling the magic flow through them as they plumped up slowly. She pinched a nipple lightly, making Sweetie cry out.

"R-rarity? What are you doing?"

"Shhh, don't worry Sweetie, I'm going to help you with this. And I promise it'll feel nice. Is that okay with you?" Rarity stopped her motions for a moment as she looked at Sweetie, waiting for confirmation. As lust addled as she was, she still had her morals, as stretched as they may be at the moment, and would respect her sisters wishes. Sweetie was quiet for a moment, looking Rarity over up and down, lingering on her cock for a bit, before staring into her sister's blue eyes, and nodding.

Rarity smiled warmly, before turning on the bed and looking at her little sisters dick. It was still growing, nine inches now, and was drooling plenty of precum all over the place, mixing with Rarity's. She took hold of the cock, and started jerking it. She bent down, and locked lips with her sister, pushing her tongue into Sweetie's mouth, and gently wrestling with Sweetie's tongue. Sweetie moaned at all this, her right hand reaching up to hold the back of Rarity's head, the other groping her own breast. This being her first time, it was no more than a minute before Sweetie's hips started bucking, and cum shot out of her cock. Not a lot, but a good healthy amount for her first. Rarity pulled back out of the kiss and smiled. Sweetie Belle's breathe was hard, and she smiled back in bliss.

"Sweetie darling. Pardon my language but, I'm going to fuck you now," Rarity got all the way onto the bed, grabbed Sweetie's legs, and hoisted them up, positioning her cock towards Sweetie's vagina. Sweetie's cheeks flushed bright red, but stayed silent as she allowed her sister to do as she pleased. Since this was her first heat, there were no worries of pregnancy. The first heat was more like puberty, allowing the body to grow and develop into adulthood. Sex helped the process greatly, and the more partners one had during the first heat (or the more a single partner could put out) the larger and more developed the mare would be by the time it ended. This was why Rarity ended up so large compared to most ponies.

Rarity slowly eased her cock forward into Sweetie's marehood, her cock slick with cum allowed it to part the lips and slide in without trouble. Sweetie was incredibly aroused at this time, and she was loose and well lubricated, allowing the cock to glide in effortlessly. Rarity slowly inched in, pushing as far in as she could. A bump formed in Sweetie's belly as she pushed forward, growing larger. Rarity hung up on her enlarged medial ring for a moment, pulled out a bit, and then thrust back in, pushing it all the way in suddenly. Sweetie gasped loudly as her belly suddenly bulged with her sisters massive cock, pleasure rocking her body. Rarity was quickly losing herself, and gave her sister no time to get used to the sensations, pulling her cock out just before the ring, before thrusting back in, falling into a steady, fast motion. Sweetie moaned and gasped loudly as she was pounded, grasping her breast in one hand, and her dick in the other, jerking it wildly.

Gasping and moaning, sweat forming on their fur as they lost themselves in each other, Sweetie's belly slowly filling with Rarity's pre. Rarity thrust faster and harder, eventually losing rhythm as she got closer to orgasm. Sweetie came multiple times, her cock and balls growing larger and putting out more cum each time. Eventually, Rarity was hit with her orgasm, the cockhead flaring in Sweetie's womb, before a wave of cum flew out. Sweetie felt a warmth spread through her as her belly ballooned outwards to make room for her big sister's seed. Sweetie came again, hard, shooting cum into the air. By the time Rarity stopped cumming, Sweetie looked several months pregnant. Sweetie smiled brightly at her, rubbing her engorged stomach fondly. Rarity felt that it would be enough to give her sister a headstart in development, but she still felt horny, she wanted more, and started pumping into her sister again, determined to make her little sister bigger.

Author's Note

A little less extreme than Big Pones, and no human this time. I was attempting to make more chapters for Big Pones, but after typing out three seperate ideas all involving Rarity as the subject, I decided it would be better to just make a different story about her. Expect lots of fun things from this.