Yamaries should be a normal eighteen year old heading off to college. But Yamaries is no normal eighteen year old. She is possessed by a demon who inhabits her body. However, the charismatic Mammon is also no normal demon, and he and Yamaries fall deeply in love. Together they rescue Yamaries' grandmother and then have to face their most dangerous mission: to rescue her grandfather. This involves returning to Mammon's home and, as he is the prince of hell, this only means one thing. A descent into hell.