Under pressure from her mother-in-law to produce a grandchild, Sumire is ordered to abstain from sex until a hot-spring trip a month later. But on the day of the trip, her husband refuses her advances, while his father is likewise rejected by his own wife. Both left painfully horny, Sumire and her father-in-law head to the baths to cool off. When he accidentally sees her seductive body in the water, he can no longer contain his desire, leading to repeated creampies and the fear that he may have impregnated her.