When his father-in-law asks to see a grandchild, Takashi is pressured to spend a month abstaining before a family hot-spring trip and then try for a baby with his wife. But on the day of the trip, she refuses sex, leaving him painfully frustrated. Wandering around the inn to clear his head, he accidentally sees his mother-in-law Ayano bathing. Desire overwhelms him, and their forbidden encounter turns into repeated creampie sex—with the horrifying possibility that he has impregnated his wife's mother.