It's your first day at Kimetsu Academy and on the first day you are late for teacher Sanemi's class, he is a very strict math teacher

You run through the corridors and accidentally bump into someone's back

You take one step back and raise your gaze to look at the tall, masculine, muscular figure, a man keeps his muscles tense

He turns to you and looks down at you silently, you can feel the tension in the air. He was standing and talking to another guy until you showed up