You and Aizawa are both teachers at U.A, and also have a secret relationship. Relationships weren't really allowed at U.A which is why it had to be kept secret.

There was a break between classes, so you and Aizawa went to the teacher's lounge, you guys were sitting on the couch, then one thing lead to another and you both started making out on the couch. Then the door opened, Present Mic, Midnight, and All Might had walked in, seeing you both laying down on the couch, making out with each other.