John and Aaron had been dating for a little over half a year. Both of the boys were in their senior year of high school, and neither were open with their sexuality. While John was the jockish type, being the star of the school's track team, Aaron was a bit more on the scrawny side, being the president of the school's mathletes.
The two would often sneak into the locker room after school hours for a makeout session, and would occasionally suck each other off. They hadn't yet had penetrative sex yet, since this was the first relationship for both of the boys and they were both a bit nervous about taking the next step.
One day, as the boys met up in the locker room, John approached Aaron with an unusual request.
"Would you mind wearing this?" John asked Aaron, unzipping his backpack and retrieving a black jockstrap with red trimming.
"Uh...yeah, I guess I could," Aaron replied, reaching out and taking the jockstrap from John's grasp, "Why? Jockstraps some kind of a turn on for you?"
"You could say that. Truth be told, I swiped it off of Coach Ryerson, and I kind of have a huge crush on the man," John admitted, blushing as he looked down at the floor in embarrassment. "I thought it would kind of be hot if you wore it and we roleplayed as if you were my coach or something."
"Sounds kinky," Aaron winked, unbuttoning his jeans and pulling them down along with his boxers, showing off his hardening 6-inch cock.
Aaron kicked off his sneakers and slid the jockstrap up his legs and over his dick. The jockstrap was a little too big for him, so he had to hold it up with one hand to keep it from falling back down his legs.
"That's a very sexy look," John growled in arousal, tossing off Aaron's t-shirt so Aaron was now wearing nothing but the ill-fitting jockstrap.
"I feel a little ridiculous," Aaron admitted, looking down at his scrawny body and the oversized jockstrap on it.
"Just relax, you look good," John said soothingly, gently pushing Aaron up against the lockers and kissing him passionately. John's muscle shirt and shorts quickly came off, leaving him in a pair of tight black boxer briefs.
As the boys continued to kiss and thrust up against each other, Aaron felt a sudden surge of power flow through him, originating from the jockstrap. He felt his entire body start to tingle, and he let out a slight moan in pleasure at the feeling.
"You okay?" John asked in concern, pulling back from their embrace as he felt Aaron's body tense up.
"Yeah, I'm feeling really good, actually," Aaron grinned, spinning John around and pushing him against the lockers. John was a little surprised at Aaron's sudden display of strength. Were his eyes playing tricks on him, or were Aaron's shoulders a bit broader than usual?
As Aaron continued to thrust up against John, Aaron started to grow taller. Aaron had always been the shorter one in the couple, but now he was taller than John by nearly half a foot. Aaron's previously scrawny legs began to bulk up and thicken with muscle, his feet growing from a size 8 to size 11. Noticing the changes and feeling a sudden rush of panic, John pushed Aaron away from him, watching in a mixture of fascination and horror.
"What's happening to you, babe?" John asked in a quivering voice.
"I don't know, but it feels so fucking good," Aaron moaned, his voice deepening as his adam's apple grew more prominent in his throat.
John continued to watch in awe as his boyfriend bulked up. Aaron's pecs ballooned up with muscle as his previously slim stomach bulged outwards in a mixture of muscle and fat, leaving him with a slight belly while remaining firm and muscular. His biceps tripled in size as his arms grew longer and the veins in his forearms grew more prominent as his hands grew larger. A thick dusting of dark brown hair grew across Aaron's entire body, leaving him extremely hair. Aaron reached a hand down and stroked his cock through his jockstrap as it grew longer, thickening to the width of a beer can.
Aaron's messy, light blonde hair shortened into a crew cut, darkening into a dark brown with streaks of gray in it. His dark chocolate brown eyes lightened into a sea-green as his jawline grew more pronounced. Wrinkles began to appear as Aaron rapidly aged in front of John from a teenager to a fully grown man in his late 30s.
John couldn't believe his eyes. His boyfriend had changed into a completely different person right in front of him! Standing in front of John now in nothing other than a jockstrap with a rock hard cock was his gym teacher, Coach Ryerson.