Having lost her husband, Mari lives with her daughter Yuko and her son-in-law Kyo. Yuko is often away traveling as a hobby, so Mari spends most of her time alone with Kyo. One day, an unexpected incident leads to a twisted relationship between the two. Though tormented by guilt towards Yuko, the two are unable to suppress their aroused bodies and promise to "make love to each other on the night Mari puts on perfume." And today, in front of Yuko, who could not possibly know about their promise, a lustful Mari puts on perfume...