With a lot of thought, Jeff decides to become younger. Not having all of his responsibility, hopefully no annoying younger sister, and having his parents just take care of him again, like the older days. He read through all the rules of it, and decided to start off by tapping the reality shift option, wanting to make sure he experiences it right.
First came the thought of how young he wanted to become, and for how long. He made sure he'd have access to the Chronivac, so he decided to start off rather young. With most of his basic functions left active, he decides to go back to the womb, at only around six weeks in.
As for how long, he wanted to wait and let it all happen around him for a while. Worst case scenario, he could revert it early if need be, so he set it to last a few years. He'd be able to experience pregnancy from the inside, even if he'd likely never experience it from the outside.
With these basic settings in place, he put in some of the others, and then hit confirm. It took a moment, but then he started regressing. His body was going backwards in time, at about a year back for each real-world minute.
Jeff took his clothes off, for the last time he'd be able to for months, and stood in front of his body-length mirror. He felt some pain in his groin briefly, and assumed he was losing his puberty status. "That hurts a bit, but it's all going to change soon!" He said, hearing his voice crack.
He reached ten years old, and was admiring how childish he now looked. His genitals were so small now! "I don't remember it being this small!" He fondled his tiny child cock a bit, taking in the feeling.
His face was turning back into an innocent child's face, as he was approaching eight. He got distracted as the door opened, and his formerly little sister came in. "Je-" She was about to yell his name, before seeing him. "Jeff what's happening to you!"
He knew there'd only be a few minutes of this, so he decided to do a bit of acting. It wouldn't impact anything... right? "Uhh, I-I don't know!" His sister was actually taller than him for once, as he was reaching seven.
He turned his body to face her, attempting to hide his crotch. His sister was confused and freaking out, with no idea what was happening. Six years old passed. "What do we do?!"
Five years old passed, and his sister was trying to figure out what was going on and if it could be stopped, meanwhile he kept the act on. Four years old. She then had a brilliant idea. Or, in her eyes at least.
"I-I think we need to go tell mom!" She quickly went out to go find her. Three years. "Mom isn't here! She's out at the store!" She panicked even more. While the two had their fair share of disagreements as siblings, such as earlier with the transformation thing, she genuinely seemed scared of what was happening to him. Two years...
The last bit of the transformation sped up, and Jeff would be too young to reasonably be able to continue communicating with her normally. His sister picked up the baby Jeff, who was still acting, and kept wondering what could've happened to him, before scaring herself with the thought of it happening to her next!
Before long, he became young enough to be returned to the womb. His vision went black, and he reappeared inside... the transformation having successfully reverted him.
In the small space, he was able to see surprisingly well. It had a bit of an orange glow to it, and he looked over his new body for the time being. The umbilical cord blocked his view of 'down there' for the time being, but he could somewhat get around it, which showed his genitals hadn't developed yet. It was a bit hard to see still, and the lighting didn't help much
He had the Chronivac, surprisingly floating in there with him. He couldn't reach it though, so he couldn't do anything but wait for now...