In the car ride home, Adam could hear his sister fiddle with the device in the back. "Would you shut up?"
"Adam," their mother warned. "She's eight years younger than you, let her have her fun."
He looked back from the passenger seat to his sister, who poked her tongue out at him, and continued messing with the device. It made a sound as it turned on. She squealed in delight. "Look, bro! It's me!"
Sure enough, the screen showed a perfect 3D mesh of his sister's body. With a click of a button, the skin rendered over the top, and Adam was stuck looking at an uncannily accurate digital version of his sister. "Are you sure you should be playing with that?"
"Come on, you play with videogames all the time." She moved the controllers and hit a few buttons. "Ooh, it says I can edit myself."
Adam rolled his eyes, glancing back out the front. There were a few moments of silence, where he swore he could hear the cogs turning in her mind. "What are you doing?"
"I'm gonna make my boobies all big!" There was a pause, and a gasp, followed shortly by a whine. "Aw, it didn't work."
Sighing, Adam turned back to see what she'd done, only to stop at the sight that awaited him. As a ten-year-old, she was just on the cusp of puberty, which meant she'd only just began to develop the small lumps that would one day blossom into breasts. Or, at least, that was the case before. Now, however, Adam stared at his sister, just the same in every way except for the two enormous jugs that filled up her top. Each globe was as big as a basketball, and just as perky, keeping a perfectly spherical shape as they defied gravity. Distracted by his sister's incredible, impossible tits, Adam didn’t realise she'd turned the diagram to face him.
"Why's it not working?" she whined. "I tried to make my tits bigger, but they're just the same as always." He startled as he realised the model on the screen matched her new body exactly.
"W-what do you mean?" he stammered. "Your breasts grew massive!"
She frowned at him. "No, they didn't."
He felt as slap on his arm from his mother. "Don't tease her, Adam. You know perfectly well she has a disorder."
He stared incredulously at his mother, who sighed at the blank expression on his face. "Honestly, have you not listened to a word we've said? We've been trying to educate you on your sister's HMPPG for years, but I suppose it was too much to show the bare minimum respect."
Adam's head swam. He pinched the bridge of his nose. "What… wait, what does HMPPG stand for?"
His mother gave him a look. "Hyper mammary pre-pubescent growth disorder."
"What?"
"She grew large breasts before she'd started puberty. There, do you understand now?" She shook her head as she turned back to the road. "You're getting grounded when we get home, mister."
Although Adam was indignant at his punishment, he still couldn't get the fact that his baby sister had suddenly grown tits in a single moment, and yet only he was the one who thought it odd. He turned back to Coral. "Hey, could I see that device for a minute?"
Shrugging, she held it out to him, but before he could grab it, a small spark of electricity shot out and zapped him. He tried again. The same thing happened. Coral giggled. "It doesn't like you."
Adam was about to dismiss the thought when he remembered the words of the shopkeeper. If you do not believe in magic, it will not believe in you. Was that a roundabout way of saying he couldn't use magic, just because he told his sister it wasn't real? And, oh god, that meant that the controller he gave Coral really was magic. He mentally cursed. Of course, the 10-year-old was given the godlike reality-altering device.
Worst of all, only he knew it. Only he could see the changes happening around them, and yet, he was powerless to stop it. Seeing is believing, the shopkeeper had said. Well, he saw it, but he couldn't believe it.