A daughter and her husband return to her parents' home to give birth. In place of his pregnant wife, the son-in-law helps his mother-in-law Maiko with the housework. Unfamiliar with the chores, he hurts his finger. Maiko reflexively bites her son-in-law's finger to stop the bleeding. Seeing her son-in-law's surprise, Maiko comes back to her senses. That night, unable to sleep, the son-in-law is gazing at his finger that has been licked in the kitchen when Maiko comes in wearing light clothing. Seeing Maiko, the son-in-law gets an erection without thinking. Maiko is pleased that she has become aroused herself and buries her face in her son-in-law's crotch...