Momoko has been married for three years and lives happily with her husband Keita, who is five years younger than her. One day, her father-in-law Tadanori, who has been living in retirement, suddenly shows up without any notice. Tadanori has had his eye on Momoko for some time, and when Keita is away he starts to flirt with her. Momoko has been having trouble conceiving, so Tadanori begins to touch her body, telling her that it's "fertility treatment." Even though he knows it's wrong, Momoko's sensitive body twitches and reacts...