Reina is under constant pressure from her mother-in-law to produce a grandchild and is ordered to abstain from sex until a fertility-focused hot-spring trip one month later. On the day of the trip, however, her husband refuses to sleep with her. Her father-in-law is likewise rejected by his wife. Both left desperately horny, Reina and her father-in-law head to the baths to calm down. There, he happens to see Reina's sensuous naked body in the water and can no longer contain his desire...