A married woman named Mariko was desperately horny due to her sexless relationship with her husband. One day she discovered that her son-in-law Masashi was also masturbating out of frustration. When she caught a glimpse of his enormous cock, she became infatuated and decided to use him to satisfy herself instead of her daughter. She began seducing Masashi secretly, both during the day and at night, regardless of the situation. His resistance crumbled under the alluring scent and sensual touches emanating from his stepmother, and he found himself unable to resist her advances...
