Four years into their marriage, wife Ayumi lives peaceful days with her loving husband. However, Ayumi has a problem. Sex with her husband is bland, and her body isn't satisfied. One day, her father-in-law comes to visit Tokyo for three days and stays at their house. By chance, she encounters him after he's taken a bath and sees, for the first time, his large, manly penis. It was the moment Ayumi's unsatisfied body caught fire…
