ai mukai, a newlywed, is pressured by her mother-in-law to have a grandchild. one day, her mother-in-law suggests a hot spring trip. eager ai agrees, but is ordered to make a baby at the hot spring and is even made to drink a traditional chinese medicine tea that boosts libido. on the day of the trip, the effects of the tea leave ai unsatisfied with sex from her husband. meanwhile, her father-in-law, vigorous and full of energy, tries to have sex with his wife but is rejected. both frustrated, her father-in-law accidentally sees ai naked and can't hold back.
