Young Hwarim, who freed Jin—a snake spirit sealed by his shaman grandmother—loses control of his body, and his grandmother sacrifices her own life to save him. Years later, Hwarim, now a high school student, lives in hiding from Jin, who is still relentlessly searching for him. Then one day, Bong-gil, a student at the same school, has his body possessed by Jin, and Jin attempts to use Bong-gil to find Hwarim…