A married woman named Saya lives together with her husband and his parents in a two-family home while working as a full-time housewife. Occasionally, she would take up modeling gigs wearing swimsuits through friends' introductions. One day, her son-in-law Hakufu discovered that he couldn't maintain a healthy marital relationship due to his excessively large penis size, which he had been masturbating using one of Saya's old swimsuits... As if hypnotized by his enormous member, Saya claimed she was doing it all for her daughter and persistently teased him both during the day and at night. Despite trying to resist, Hakufu eventually succumbed to her seductive advances and spent his days being taken advantage of by this wanton woman.

娘夫婦と同居して二世帯住宅で暮らすさゆり。専業主婦の傍ら、知り合いの紹介でたまに水着のモデルをしながら過ごしていた。そんなある日、娘婿の邦夫が彼女の使用した水着で自慰に耽っており…。どうやら、彼がデカチ〇ポ過ぎて夫婦生活がうまくいってないというのだ。だがあまりの巨根に目を奪われたさゆりは「娘の為」と言い聞かせ、昼夜問わず彼を執拗に誘う。あまりの妖艶な痴態にお預けの日々を過ごしてた邦夫は抗えず…。