Nothing, just her brother writing in a script booklet

She opens the door to her brother's room, and spots him at his desk, the script he picked up earlier and a pen in his hands. She gave him a look of disapproval, "Hey perv, what're you doing, reading erotica or something? Could at least stop your moaning, I could hear you last night." And gives an indignant sneer. Chris scowled at her, running the pen through the book, Kirsty thinking that he's trying to ignore him. Kirsty reached behind her, and tugged at her panties under her pants, wrenching them up. Kirty's eyes widened in surprise, feeling the elastic of her grey panties yank up against her crotch and in between her buttcheeks. Her hands were gripping tight on the garment, and looked like they wouldn't obey her to drop them anytime soon. "W-what am I-" Suddenly, she felt a tingling sensation, an alien pleasure that she never before experienced. She felt the panties bunching against her crotch, feeling dampness. pleasurable tingles went through her as she continued to yank them, wiggling her ever-plump bubble-butt and making it dance around from her stooped state, pants falling and leaving her in her tugged up skivvies and shirt. She tried to stop herself, but the more she thought about her brother watching Kirsty humiliate herself like this sent her higher amounts of bliss travelling through her body, making her tug harder, and making herself wetter. Kirsty realised; from her research on porn and how to get off, that she may be subject to being turned on. All of a sudden, a mixture of conflicting emotions afflicted her mind; This is great! I'm not a sexless flesh robot after all! and Oh no, what turns me on is humiliating myself in front of Chris?! No, that's too cruel of irony!

She looks up at Chris, who seems to be watching her now, laughing at her plight, which makes Kirsty make a sudden involuntary moan and wiggle more. "Looks like Buttslut is having a tough time controlling her urges again~" And began writing in the script once again, as if she wasn't there. "What did you-!" Kirsty started, until she remembered that was what everybody called her. Although born Kirsty, ever since her wide load sprung forth, she was subjected to such a dirty nickname. Even their parents called her that! But it was her fault, really; She encouraged it by her speech impediment of talking in the third person, calling herself 'Buttslut' every time she talked about herself. "You know Buttslut doesn't like that name...!" Kirsty whimpered, feeling hot again at the idea of being embarrassed in front of her twin. "Why is Buttslut giving herself a wedgie? Are you doing thi~is?!" She tries to yell angrily, but was overcome by a strange sensation. Like a bomb going off against a dam, and a massive flow of pleasure drenched her in ecstasy, she fell on the floor, humping the air and moaning like crazy, her traitorous hands now giving her a frontal wedgie to rub against her vagina harder.

After about several minutes of coming down from the greatest ride she ever been on, Kirsty noticed that her hands have stopped, and her brother looking at her with wide saucers for eyes. "Whoa, what brought that on, Buttslut?" But Kirsty was still having trouble speaking at the moment. What came out of her mouth was just elongated words broken apart by rapid breaths forming a drawn out question, "Whaaat...did...yoouuu...dooo...tooo...Buttslut?"

Chris smirks from his comfy swivel chair, looking down at her and trying to cover his crotch region with the script pages.