Hwalim is a young girl who accidentally releases Jin, a serpent King her shaman grandmother had long sealed away. Jin seizes Hwalim’s body, and to save her granddaughter, the grandmother sacrifices her own life. Years later, now a high school student, Hwalim is still living in hiding, constantly on the run from Jin, who relentlessly seeks to reclaim her. One day, Bong-gil, a boy who attends the same school as Hwalim, becomes Jin’s new host. Using Bong-gil’s body, Jin begins closing in—determined to finally track Hwalim down.