Yumiko has been married to her husband for 20 years. Since their son grew up, the couple has been having sex. However, she is not satisfied with her husband's declining physical strength. Still, she wants to climax through sex. A few days later, her husband suddenly says he is going golfing the next day, and Yumiko consoles herself in the kitchen. When her son comes home, he is surprised to see the kitchen and runs into his room. The next day, Yumiko is cleaning the house. The son can't hold back after seeing his mother masturbating the day before and her shaking ass...