As a young child, Hwarim accidentally unleashed Jin, a snake god sealed away by her grandmother, who was a powerful shaman. Jin took possession of Hwarim's body, and her grandmother sacrificed her own life to save her. Years later, Hwarim is a high school student living in constant fear, trying to hide from Jin, who is still tirelessly hunting for her. One day, Jin possesses Bong-gil, a student at Hwarim's school, and uses him to track her down.