After losing her husband, Mari Fujitani began living with her daughter Yuko and son-in-law Kyō. Since Yuko frequently travels and is rarely home, Mari often finds herself alone with Kyō. One day, an unexpected incident sparks an illicit relationship between them. Despite feeling guilty toward Yuko, the two are overwhelmed by their desire and make a secret pact: whenever Mari wears perfume, they will give in to their passion. To this day, while Yuko remains unaware, Mari applies her fragrance and spends the night with Kyō.