Kris,a normal human being.loves Seohyun and so does she.They were couple for four years.Kris and Seohyun were deeply in  love and lives happily.Everything was fine until Seohyun met an accident one day.She was in coma and in critical condition.No one can do anything to save her and not even the doctor.Kris does not know what to do and he is deadlock.He was so desperate because she does not want to lost his first and eternity love,not now,he is not ready for that.

   He was all wrong when one day the demon offered him to save Seohyun's life and in return he must leave his human life,his friend,his family and his love-Seohyun to be a part of the demons.It was hard for him to make a right decision but for the sake of Seohyun,he is willing to do anything including ruining his own life and being the most violent demon and he is Kris-the angel of darkness.