Well, you think Brett will appreciate the "anonymous gesture". But after you and your new boyfriend Zach leave the school, someone other than Brett opens the locker. And that someone is none other than Greg, the biggest bully in school.
"Let's see what that twerp has in here," Greg mutters to himself. He reaches into the locker and pulls out some papers, a book, and ... ugh ... a pair of underwear. A dirty pair of underwear. "What the fuck? This has cum on it. Sick!" he nearly yells in revulsion. He had no idea Brett was a pervert. All the more reason to beat the kid up.
He throws the underwear back in the locker, but finds that some of the cum had rubbed off on his hand. "Ugh," he utters, holding his hand as far away from him as possible. "Disgusting." He quickly turns and heads to the sink in the corner of the locker room. He then turns the water on and is about to put his hand in the water, but notices that the cum is gone. What had happened to it?
Then he feels a strange sensation. Like he had just gotten done with a fierce workout, but without any of the sweat or tiredness. He turns off the water from the sink and looks at himself in a nearby mirror. The reflection shows a much sexier version of himself. With a body like this, he'd have no problem at all getting any girl into bed with him. But then something happens to his head. It feels fuzzy. And suddenly, he realizes that he likes guys. Girls don't do anything for him anymore. He's gay, and he's totally fine with it. He knows it should freak him out and disgust him (after all, he made it a point to bully fags, especially that Zach kid), but it doesn't. It feels ... normal.
But then his thoughts shift to his friends, some of which he now finds he's attracted to. They're aggressively homophobic. He's fine with being gay, but he's sure that they aren't. Should he keep his new sexual orientation a secret? Or tell them? Or maybe ...
He turns back towards Brett's locker. It's pretty obvious by now that the cum he found on Brett's underwear had turned him gay. Maybe if Greg puts the cum on his friends ... maybe they would change like he had. If they were gay and were fine with it, like he is now, they could all remain friends.