My wife and mother-in-law are huge fans of the hot-spring idol group Sokai Onpu, so when they learn the group will visit a nearby resort, the four of us plan an overnight family trip. My father-in-law asks me to use the romantic setting to try for a baby with my wife and orders a month of abstinence. But once there, my wife is absorbed in the idols and baths and ignores me. Frustrated, I wander the inn at night and accidentally see my mother-in-law bathing. I lose control, repeatedly creampie her, and end up impregnating her.