Sayuri lives with her married daughter and son-in-law in a two-story house. Besides being a full-time housewife, she occasionally models swimwear through an acquaintance's introduction. One day, she discovers her son-in-law, Kunio, masturbating with the swimsuit she wore... It seems his enormous cock is the reason their married life isn't going well. However, Sayuri, captivated by his massive size, convinces herself it's for her daughter's sake and relentlessly seduces him day and night. Kunio, who has been enduring these days of being treated like a sex object, can't resist...
