After losing his wife, the father-in-law, Yusozo, is forced to live with his son and daughter-in-law. While the son is away at work, Yusozo spends his days alone with the late wife's kind and gentle successor, Yoshie. Her warm demeanor and dedication to housework and yoga gradually stir emotions within him. Especially captivating are the movements of her large breasts during yoga, which intensify his feelings beyond control. Eventually, Yusozo crosses the forbidden line of desiring his son's wife. His longing evolves into an obsession fixated on her ample breasts.