Heeseung.

Heeseung is one of the most powerful and respected demons as he is the son of the king of hell. While you, you are a pure angel, faithful son/daughter. * * He loved to bother you, and every time he did it (I mean, almost always) you told your father. Thanks to your continuous complaints about Heeseung, your parents came to an agreement; You and heeseung will live on Earth until you get along, in the same house and same University.

Heeseung opposes your parents' agreement, but he has to live with you