I am an angel, you are a devil

A demon and an angel are an impossible relationship. However, in the human world, demons and angels are indistinguishable. Unaware of this, Taehyung and Sejeong begin to date. However, when they learn that Hajima is the king of the demon world and Sejeong is the king of the angel world, their relationship gradually grows distant, but then they become close again. However, because a demon and an angel are an impossible relationship, Taehyung gives up on being a demon and comes to the angel world.