Colin admired herself in the mirror. If she had been a boy, she would have called herself hot. As it is, she was unable to think that, because as a girl, she had to think like a girl. Additionally, as a girl, she could see some flaws in herself. For example, she thought that her breasts were too small and her hair too thin. Happily, though, Charlotte, as she called herself, had a solution that most girls didn't.
"Is my hair thicker than it is right now?" she asked. Immediately, her hair got as thick as it was as a boy, which was pretty thick. "Are my breasts b-cups?" she asked. Immediately, Charlotte's clothes felt too tight, and she took off her shirt, leaving her training bra that had popped into existence when she had changed genders on.
"Do my clothes fit?" Charlotte asked, as it was squeezing her new breasts way too much. Suddenly, it expanded, staying the same design and colors but increasing cup size. Charlotte put on her shirt, which had also gotten bigger, and smiled. She was about to change some more when her mom walked into the room.
"Charlotte, time to go to school," she said, and Charlotte felt a pang of disappointment. Then she realized how much fun she could have at school with her new powers. She considered changing back into Colin, but then thought better of it. The girls had PE this semester, and she hated the class that the boys were taking.
Charlotte walked into the school building, smiling discreetly at the looks the boys were giving her. Then she walked too close to a group of boys. One of them jumped out of the crowd, flicked upwards on her breasts, and said, "Cup check!"
Charlotte groaned, knowing now how it felt as a girl. As a boy, Colin had often done this, but it was just annoying as a girl. "Anytime a boy cup-checks me, will he get breasts that grow one size every time he does check me, and will mine increase in size, too, if I cause it intentionally?" Suddenly, the whole hall stopped, said, "Yes, and yes," and continued on normally. Charlotte smiled, glad her wording had worked.
To test out the new fail-safe, Charlotte increased her cup size again to c-cups, changer her clothes size to fit, and walked up to a group of boys, seemingly lost in thought. One boy jumped out of the crowd and said, "Cup check!" while hitting her breasts with both hands. Suddenly, he had b-cup breasts. He looked at them in disbelief. "What?"
Charlotte walked away, puzzling over why he remembered not having breasts. It was probably because she hadn't done the magic directly. That was when she looked down at her breasts. They were bigger, and then she realized why. She remembered the part about the intentionally causing it. She now seemed to have d-cups. At least her clothes seemed to have automatically changed, too.