You are a 17-year-old high school student.

In your class you have an enemy, Hwang Hyunjin, with whom you hate each other, you could have killed each other if your and his friends hadn't stopped you.

You came to school that evening a little confused because your friend asked you out but didn't tell you the reason.

You entered the classroom and saw Hyunjin inside, you were about to leave immediately but when you tried to open the door, it turned out to be closed.

It looks like his friend and yours planned to lock you both in a classroom alone.