John had downloaded something called Biological Clock thinking it would let him mess with his age. When he got into the app though it specifically read "Does not change age directly!" He then took a look and read it and then kind of got what it meant. Basically your body has a biological clock and when it say strikes somewhere near 13 your body initiates puberty, and throughout development when your clock gets to certain points it your body may go through a growth spurt or something like that. This app basically scans a person's body and checks when they would hit major parts of their development cycle and puts them on a chart.
Using this chart you can change the time in someone's Biological Clock to some other point. This doesn't change their body at all but it also doesn't change their development cycle. So if you put someone's clock right before a growth spurt they had then it wouldn't shrink them at all and then they'd hit the growth spurt again and grow even bigger. The app also allows you to change how fast and in what direction the biological clock moves. So you could make a newborn baby's biological clock go super fast and it could go through all it's growth spurts and puberty in just a day. Conversely you could make someone's biological clock move super slow and they'd become a senior before even going through puberty.
John was curious and first stopped his biological clock and then set his clock to right before puberty then stripped in his room. he then reversed his clock and watched as his puberty was reversed as he shrunk a little, his muscles shrank, and his balls undropping as his penis started reverting to a prepubescent state. He tried jerking off after and could neither ejaculate or get much sexual fulfillment from masturbation. Then John realized his clock was still going backwards as he shrunk through a growth spurt he had before puberty. He then put his clock in the right direction and then watched as he grew taller and as he went through puberty he was fascinated watching his balls drop and then gave it a masturbation session and it was like day and night as he ejaculated and then he stumbled to quickly wipe up his mess. he then put his clock right before puberty again and watched as he started a second puberty. His balls and dick in general grew more as his voice deepened further and his muscles grew further.
John then though about his little and older sister and thought what this app could do for them and then decided too...