He kept scrolling through the options. There were several that caught his attention, with the options getting better and better as he scrolled down. He eventually found one he knew would be a great method of payback; One that'd impact her life quite a bit, and change her in a way where he knew he would be dominant. Turning her into a toilet.
He already felt the need to pee, and decided it'd be perfect. Eagerly going into the option, he started putting in the settings. He decided to choose her vaginal entrance as the point of change, knowing that he'd have even more fuel later on. "This could end up really fun!"
To slightly reduce... incidents, he decided to make it so that not everyone would know she has it; With the reality shift feature, he set it so that only those she'd have directly told would know, and included himself just in case. He hit confirm, and the chronivac did it's thing.
With the changes in effect, he knew it was time to find his sister. His first guess would be in her room, so he went there first. "There she is!"
Entering the room, she looked at him. "Jeff! What are you doing here?" To test if it worked correctly, he decided to just answer honestly. "I just need to pee, that's all." She seemed annoyed, but then got up. "Alright..."
She pulled her pants down, alongside a diaper. He was initially confused, knowing she didn't wear diapers; Before he could ask, however, new memories from the altered timeline entered his head, which he guessed was the Chronivac's doing.
At first, she didn't use to wear them. However, people kept constantly using her as a toilet to the point of eventually damaging her own bladder, and she ended up unable to hold it sometimes. After several repeated incidents of this, she ended up wearing diapers full-time to ensure that she wouldn't pee herself in public or during the night.
Blushing, She stepped out of the diaper, revealing her naked bottom for Jeff to see. She didn't let him stare for long, though. "Please get it over with quickly..."
He understood, and pulled down his own pants, before picking his little sister up. His penis stood erect, and he slid it in; Despite her being quite a bit smaller than him, it fit pretty much perfectly, and was relaxing enough for him to pee in a situation he normally wouldn't.
He let it all out inside his little sister, something he never thought he'd do. But it soon ended, and he knew he'd have to put her back down. He quickly pulled his pants up while doing so, at least trying to hide it slightly.
"Thanks Sis." He went back to his room. He had mixed feelings about the encounter, but knew that she thought it was all completely normal. He thought back on what he got out of that; Although he was capable of peeing inside of her, he noticed that it wouldn't be easy for a girl to do it, nor would it be easy to poop into her.