Chastity's younger 12-year-old brother Bradley was standing in the archway of her room holding her stone in his hand. "Give me that back!" she screamed. Bradley dodged out of the way, saying, "I wish I knew what you were so angry about, Sis." Suddenly his eyes shot open with knowledge about the stone.
Not wasting any time, seeing Chastity rebound to go and strike him, he cried, "I wish I was the most muscular kid in school!" His clothes ripped off his body as his muscles rapidly inflated, making Bradley look like a young powerlifter. His ripped up tatters reformed around his genitals, becoming a snug Speedo. Bradley lifted his powerful arms and pushed his sister onto her bed. Chastity couldn't hear him as he muttered under his breath, flexing in her mirror. Suddenly the muscular boy started rapidly aging, his face becoming angular and mature. His muscular body became taller and even bigger through puberty, his penis springing erect in his snug Speedo and straining the semen drenched fabric as it elongated, becoming thicker and more veiny. Thick pubes developed around the base, sprouting up to a cute happy trail all around his belly button leading up to a proud thicket, and his arms and legs became hairier as proud bushes of hair emanated from his armpits.
Chastity was both frightened and attracted to the gorgeous hunk her kid brother had become. As he calmed down from the overpowering arousal caused by his rapid aging, Bradley turned to his sister. He smiled a smile that would make any girl weak at the knees.
He spoke in a sexy baritone: “So, Sis, you want this stone, huh?” Chastity nodded. “Well, I have a deal for you. I love this body and want to use it. Here’s the deal: if you help me navigate high school for two weeks, pretending I’m a cousin visiting town, and you allow me to use this stone however I want, I promise I won’t use it on you, and when the two weeks are up, you can have the stone back. You can make me 12 again, but you have to leave my memories intact and keep me as the most muscular kid in middle school. Do we have a deal?”
Chastity thought it over. What other choice did she have? She said “Yes” and shook Bradley’s hand.
“Great,” he said. “Now help me find some temporary clothes. I want to go out and buy the most stylish stuff money can buy.”