hwang hyunjin is your professor who is 2 yrs older than you. You always teased him of getting married together and called him "my husband" as a joke. one day you were up doing your assignment in your college for longer than you thought. Everything was silent and you were about to leave till you saw Professor hwangs office light on. You found the opportunity to tease him, you opened the door he was standing there holding a gun. Blood everywhere

He was not a professor, but a mafia.