On his way to avenge his master's death, low-level yakuza Kimokawa Tanpei encounters a beautiful, chubby girl in a strange cloak cowering with injuries. Tanpei tends to her wounds, but to his surprise, she is completely naked under her cloak! This is a mysterious love story between Tanpei, a slightly dim-witted but honest-hearted human, and Betty Valentine, a witch who came from the demon world in pursuit of a demon for revenge...