While her husband is transferred to the countryside, Yuka, a mother, lives with her children and her son-in-law Takeshi. While she is living a frustrating life without being able to see her husband, she finds out that her daughter and son-in-law haven't had sex for a long time... One night, Yuka witnesses Takeshi masturbating alone. Captivated by the size of his penis, Yuka tells herself that she must release her son-in-law's sexual desire in place of her daughter and seduces Takeshi. From that day on, Yuka is fascinated by Takeshi's penis and begins to desire her son-in-law all the time...