Jon took it out of his back-pack and showed it to Karyn. Before he could say or do anything, she had grabbed it from him.
"What are you doing?" asked Jon.
Karyn held the rock and said "I wish, that for one hour... no, scratch this... I wish that until he's learned his lesson, Jon would become my little sister..."
Jon's eyes went wide as he heard Karyn speak. He knew whatever was wished HAD to become reality and he was doomed to spend time as a... GIRL! He felt paralyzed and in his panicked mind he only thought how much he didn't want that to happen. His eyes scanned Karyn quickly head to toe and then back up again. His gaze stopped at her recently magically-enhanced chest.
"Fuck... Will I have..." he thought, gulping loudly. "breasts?"
Karyn noticed Jon's gaze. "Yes," she decided. "he really does have a lot to learn."
And so she continued her wish.
"... would become my little sister, whose breasts only just begun to grow last year but are already my size..." she paused for a fraction of a second. "... and still going strong."
Jon heard the last part of the wish. He didn't want to think what it meant. He felt the tips of his fingers and toes start to tingle and he knew one thing - there was no point of resisting the magic. The wish will have it's due.
He closed his eyes and felt himself faint.