“…turn my butt cheeks into massive breasts.” Your sister told you, She then turned around and pointed to her rear. “Go on. I already made a change to you so go ahead.”
You asked, “Sarah? Are you sure?”
She looked over her shoulders and nodded. “Just do it already! It having breasts before butt cheeks sounds both fun and quirky!”
You sighed and then told her to take off her shorts and undergarments to see her naked rear end. Breathing in you took aim at the right cheek. Then you made sure that the grow button was hit and then you finally pulled the trigger. The first thing that you saw was that a red nipple was growing on the center of her skin grew a red nipple. As you held the trigger you watched her left breast grow out at a steady pace. You watched as her entire left side of her rear widen out to fit the new butt breast that was growing. It didn’t take long for the new breast to hit the C cup size. You continued to hold onto the trigger as you could her your sister hold back a gasp and slight moan.
Soon you had it hit the D cup size and watched it grow bigger and unknown to you your sister Sarah could feel it fill with something yet her new growing half of her booty did not fall down. She could feel milk, breast milk fill her rear end where the breast finally hit about half the size of a beach ball, one half the size of one of your breast balls. “Keep going till it’s the same size of yours,” Sarah told you.
You nodded as the breast finally reached a full beach ball size, in other words, one foot round. At that point you let go of the trigger to see the new lop sided rear end. Her red nipple was around about six inches round with the center part of the nipple being three inches and was another three inches thick.
You then watched your sister put her left hand over her brand new breast to shake it. “Joe,” She started. “I still need the other one transformed.”
You nodded as took aim at the other one and fired. You once again watched a red nipple grow out on her flesh. Once a good sized nipple grew the rest of her butt cheek started to follow the nipple which took the lead. You watched a one more breast grow out as it reached the C cup range. Once again her butt breast started the fill with breast milk which only further lead to her ass cheek to grow even more. It didn't take long for it to pass the D range and broke out to be half as big as her first one.
As it grew her right side of her waist widened out to fit her new growing rear. Within a minute you like go of the trigger to have her second breast cheek to reach the same size as your nuts. Sarah reached back to grab her new butt breast and squealed in joy. "Thanks bro!"
"You’re welcome," you said. "So you got what you wanted." You gestured to the door. "I'd like to figure out what else I am going to do with the breastinator.