While her husband is away on business, Yuko is staying with her daughter and son-in-law. She is living a lonely life without her husband, but she is not the only one who is lonely. When Yuko finds out that her son-in-law, Toru, is always masturbating alone in the middle of the night, she can't help but feel that it is not someone else's problem... Yuko knows the pain of not having her sexual desires satisfied, so she tells herself that it is her responsibility to take care of her daughter, and she seduces him at every opportunity. However, before she knows it, she is seducing him all the time, wanting his big dick to satisfy her own sexual desire...