Every night, Natsuki's groin ached at the intense moans she heard and the passionate, animal-like mating of flesh against flesh. Her father-in-law may be old, but he has a strong sexual desire, and every night he embraces his mother-in-law. He's a viper-man who will remain active his whole life. In comparison, her husband is bland when it comes to sex. The frustrated wife's Kokoro gradually turns to her father-in-law. She wants to be held passionately like that. Unable to suppress her desire, she goes to her father-in-law on her dangerous day to be embraced by him...