Shoko lives with her husband and her daughter and her husband. Although her life is peaceful, she is sexless with her husband and feels unsatisfied every day. One day, she accidentally witnesses her son-in-law, Toshio, masturbating... and is Kokoro by his enormous cock, which stands out in the darkness. Unable to resist, she seduces him 24/7, wherever she is. Toshio, who has not had sex with his wife for a long time, cannot help but jump at his mother-in-law's lewd behavior, and before he knows it, he begins to look forward to having sex with her...