Brad, coming in late from class, hurries to his locker and grabs his jockstrap for wrestling practice for the next period. You watch eagerly as he goes into the locker room, and comes back out with the jockstrap just barely visible from the outside of his shorts. Accidentally, not watching where you are going, you bump into him on your way to the gym.
“Watch where you’re going sophomore! I’ll have to kick your ass if you’re not careful...”
You both walk into practice, where you notice it is comfortably warm at 98% F, and start running around the room. As you’re running, you look inside your pants to make sure the magic marker is coming to life with your body heat. To your surprise, you can see the faint writing you placed on the jockstrap just hours before practice. You start to feel lightheaded, and ask to go to the bathroom.
Just as your coach let’s you go, Brad seems to fall down from running. You can only suspect the magic is starting to work on him as well. “I’ll take him to the locker room” you chime, and head with him to the locker room.
As he pushes off of you towards a stall, and locks himself in, you stand in front of the mirror to watch the transformation begin.
The jockstrap starts to get tighter, and wraps itself around your cock like a condom, and gives you the most sweet sensation you have ever felt. From there, it grows before your eyes to a whopping 7 1/2 inches long, with thick curly pubic hair growing starting to poke out of the jockstrap.
Then, your body starts to bulk up before your eyes, muscles growing bigger, legs getting larger, and chest expanding to that of a senior champion wrestler.
The transformation makes you harder than a horse, and you can feel the orgasm coming to the end of your new found cock.
Near then end, you shoot cum all inside the jockstrap, and howl in pleasure as the semen seals the transformation now to Brad’s (your) huge body.
As you’re coming down from your transformation, you hear the bathroom stall behind you, and see a splitting image of your former body looking at you in pure disbelief.
The now former Brad starts to approach you with animosity in his eyes, but you simply push him to the ground.
He gets up and stammers, with something he needs to say on his mind.