Help finding this bl pls

It was an omegaverse manga where the omega was a janitor in the alphas school. The omega nearly gets assaulted by another alpha at the school during his heat but the ml saves him and bites his own hand instead of the omegas neck. Later on there’s a scene which is after the omega was marked, in which ml comes back from a work trip and finds out Mc is in heat. I think there was a student/mcs friend outside their apartment door as well.