Jeff just chuckled to himself quietly as he watched his absurdly stretched out 10-year-old sister eat her cookie. This Chronivac had been a lot of fun already. He decided that he wanted to try changing her again.
He set the controls so that his sister would become 10 years older, but still remain 5'8" tall as she aged. He also made sure that her clothes would grow to fit her and that she would remain unaware of the changes.
Jeff pressed the button and turned to watch as his sister's extremely skinny limbs began to thicken. Her face started to look more mature as she entered her teen years. Her hips widened and her chest started to expand as she reached puberty. Soon the changes stopped, and Jeff just stared in wonder at the very cute 20-year-old woman that his sister had become. Just like before, she was 5'8" tall, but now she had beautiful womanly curves. He guessed that she had B-cup breasts, which appeared to be supported by a bra that had appeared as her clothes grew with her. Jeff was happy to see that, as with the changes before, it appeared that she hadn't noticed anything happening to her body this time either.
Although Jeff knew that the attractive woman standing before him eating a cookie was in fact his 10-year-old sister, he couldn't help but feel a little aroused by looking at her. He was a red-blooded 14-year-old boy after all.
Jeff shook his head and told himself mentally, "Stop looking at her like that. She's your little sister. Control yourself!"
He knew that he should change her back to normal soon before someone else saw her and freaked out, but he wasn't sure if wanted to experiment on her a little more first or not. It was tempting thing, to have a Chronivac at his command.
Oh, decisions... decisions... What would he do?