Sanshiro, a young servant who has fallen in love with his master's daughter, Momoyo, torments himself with lustful thoughts while spying on the buxom young woman through a hole in her ceiling. On the day her fiancé returns from abroad to take her away, filled with despair, Sanshiro watches in amazement as Momoyo and her fiancé engage in depraved S&M activities with each other and various members of the household. As time passes, Sanshiro becomes convinced that these bizarre rituals are designed to summon some sort of demon, and he takes it upon himself to stop Momoyo's fiancé from destroying the woman he loves.