Johnny and Amy had been left alone for a few hours while their parents were out doing something. They'd been trusted with alone time more and more recently as they were older and now were trusted a bit more. Then the doorbell rang and after the delivery man was gone they found the box and saw it was addressed to them. They were curious and opened the box to see it was a remote, a usb drive, and a usb cable. They went directly to their shared computer and put it in, and the computer downloaded the files, linked up with the remote, and now there were two devices were working in tandem.
"Scanning" read the desktop application and then it read "2 profiles detected: Johnny, Amy" then it gave them the option to select a profile and Amy being a bit bigger at their age got to the keyboard first and selected herself. and it gave a wireframe scan of her body and clothes. It also had a prompt "Change?" Amy wondered what she'd look like older so she wrote in Age 24 and then when she hit enter her body felt weird. The tween felt puberty go into overdrive as she gained a foot or so in height as her hips and chest filled out considerably. The dress she was wearing had rose up just barely exposing her now stretched panties. She wasn't the most buxom of ladies having a large B-cup breasts, ended around 5'6, but her tight clothing and lack of bra highlighted her womanly features and she was a woman. Johnny blushed a second as Amy left the room as she headed to her mom's to borrow a dress or something. It left Johnny alone for a few minutes with the chronivac.