Kirishima might not be first in the class but he's way smarter than to take Bakugou at his word about exactly what he's ready for during his next heat.

Obviously this was all the fault of Katsuki's perv classmate and his aerosolized heat trigger. Once Katsuki gets his life back under control, everyone will forget all about this moment of weakness. Nothing will change. He won't let it change. After all, he's going to be the number one hero one day. Just because omegas never go pro, that doesn't mean it isn't possible, right? ...right?

Kirishima tries to help Bakugou out during his first heat, and things get complicated.

It's involuntary the way his knees seem to buckle and give out and throw him onto the ground. It takes him a moment to realize he's hyperventilating, tears running frustratingly down his cheeks as he rubs his clothed erection slowly against the carpet. / Or the one where Bakugou Katsuki is presenting as a fucking omega, and there's nothing he can do to stop it

Kirishima hates his luck. Not only is he a stupid Alpha, but his longtime crush is also an Alpha, (Except he's knot) AND he's the only guy in the world that has his ...problem. The fic where Kirishima has two knots but Bakugou is up to the challenge.