Despite the use of belittling language, all characters depicted are above the age of consent.
Sky sat down on her bed, tired from the very difficult day she's had. She lived with her parents and her little sister, Violet, in a nice home, but their parents hadn't been home in days. They were both on some business trip, and wouldn't be back for another week.
The two sisters had been making the most of it, inviting friends over to drink and play some card games almost every day, but the chores that had been piling up needed to be taken care of today, which took more out of the two of them than either would like to admit.
You know, it had always felt weird to Sky that Violet was allowed to drink alcohol now. In her mind, she would always still be her little sister, the tiny girl that grew up alongside her all her life, and who had always been so small, so... adorable. She still was quite a cute girl, of course, but now she had a drivers license, and a job at the local convenience store, and she was allowed to drink to her heart's content. Little Violet had grown up.
That thought hurt Sky a little, though she couldn't entirely figure out why. Of course she was happy her little sister was putting herself out there, seeing the world. Going to the club and making out with the first guy she'd see, like all girls her age ought to be doing. Sky winced at the thought of her baby sister with her tongue in someone else's mouth.
She kicked off her shoes, took off all her clothes and lay down in bed. Sky didn't usually sleep naked, but the summer heat was getting to her, and even under nothing but her thin blanket she was sweating a lot. She knocked on the wall next to her bed twice, like she'd do every night since she was about 8 years old. After a few seconds of silence, she heard two knocks back. Her little sister was also ready for bed. "Good night sis, I love you", they both said to each other through the wall, before Sky turned over and went to sleep.
Sky woke up an hour later, realising she had forgotten to go to the toilet before going to bed. She walked out of her room to the bathroom down the other end of the hall, past Violet's room. After having relieved herself, when she walked back past the door to her sis' room, she heard something. Her sister was making a soft mumbling noise. Was she having a nightmare? No, she didn't sound scared at all, she sounded almost happy? Maybe she's chasing squirrels in her dreams, Sky thought. She went back to back, amused at her own silly joke.
As she lay down, she realised her sister was slightly audible through the thin wall separating the two. Her mumbling sounded muffled, as if she had a hand over her mouth. Slightly concerned again, Sky put her ear to the wall, just to make sure her little sister was safe. Then she heard it. The sound of a woman caressing her cock, slowly, but loud enough to be recognisable. Her little sister was masturbating.
Immediately Sky felt bad for listening. She backed away from the wall abruptly, knocking into her bedside table, where a picture frame containing a photo of her parents tumbled over and shattered on the floor. The sound was very harsh, and the soft moans from Violets room stopped immediately. She was waiting to see if her big sister woke up from that, Sky realised.
She cursed under her breath, reaching for the photo of her parents, when she saw the other picture on the table. Her little sister, a picture from a mere year ago, stared back at her. The photo was of a young, adult woman, but all Sky saw was her little sister, looking up to her from next to her bed, smiling so innocently. That smile was the one she had sworn to protect.
Sky decided to stay put in bed without picking up the fallen picture, not wanting to risk making any more noise. If Violet knew that she'd heard her, it would only make her sad, Sky told herself. You need to stay quiet for her sake. For her smile. And sure enough, the cute whimpering of her little sis started up again after only one or two minutes.
Wait, cute? Of course, her little sister was adorable, but this wasn't cute, right? Violet let out a particularly breathy whimper, and Sky felt her own dick twitching. When did she grow hard? Sky blushed, embarrassed at her body's response to her little sister. Was she... enjoying this?
Another cute yelping noise came from beyond the flimsy wall, and Sky felt her hand closing around her throbbing dick before she even realised what she was doing. What was going on? She can't do this, it's so wrong! It's her little sister, she needs to take care of her, love her, sure, but not like this!
But, the noises were so adorable. The slow increase in speed of the noises of masturbation, the soft whining sounds her sister made as she got closer and closer to the relief she sought, increasing in pitch and volume as her desperation to cum grew, it was all too much for Sky.
Before she knew it her own hand was going up and down her dick with a furious passion she didn't usually feel when she was doing this. She looked back over to the portrait of her little sister as she imagined what Violet must look like, laying down in bed naughtily playing with herself. The thought of how wrong this all was didn't subside, but the growing lust in Sky's heart was far greater.
The moans on the other side of the wall suddenly got louder, and Sky realised that Violet must have removed her hand from her mouth. Did she want her bigger sister to hear? No, of course not, what a perverted thought. Her little sister didn't want Sky to hear, she was probably just using her other hand for something else. Maybe she was fondling her cute breasts, or caressing her adorable little butt.
Sky let out a moan of her own, unable to stifle it any longer, and for just a second she could have sworn she heard her sister go faster in response. Sky was a fool, of course. What would her sister think if she saw her right now? She'd feel so betrayed, years of sisterly love down the drain because big sis had to make it weird. And their parents? They would certainly not approve, they'd try to take her sister away. She'd never see her cute smile again.
She pushed those thoughts away quickly as she felt the familiar sensation of cum slowly making its way up through her cock, ready to shoot out from the swollen head. She was about to go over the edge, and there was no going back now. She moaned again, and again, loudly, and on the other side of the wall she heard her sister start moaning even louder in response. No, of course not in response, why would she think that? She was obviously just-
The thought was cut short as a thick rope of cum shot out of Sky, who let out one final moan so loud she was certain her sister could hear it. But instead of hearing Violet stop like she'd expected her to, Sky instead heard her sister almost screaming in pleasure, before heavily breathing. They had both climaxed, Sky knew, and the thought of it filled her with butterflies.
Fifteen minutes later, Sky still lay there wide awake, naked, covered in her own sweat and cum, too scared to move or even go to sleep. What had she done? Her sister must have heard her! Her beloved little sister must by now have known what Sky has been doing, and, that Sky then must've heard her doing the same. She must've realised that Sky came to her noises, to the thought of her, to her pretty smile in that picture, to-
Knock, knock. Two shaky, hesitant knocks reverberated through the wall, interrupting the spiralling thoughts. Sky immediately understood. She raised her hand up to the wall.
Knock, knock. "Good night sis", they both said, voices trembling.