Sumire, a daughter-in-law, is under pressure from her mother-in-law to give birth to a grandchild. One day, the whole family decided to go on a trip to a hot spring. However, in order to have a baby, her mother-in-law orders her to abstain for a month before the trip. On the day of the trip, Sumire is not satisfied with mechanical sex with her indifferent husband. Meanwhile, his father-in-law also tries to hold his wife, but is refused. The two, overcome with sexual desire, headed to a hot spring to soothe their aching bodies. And her father-in-law happens to witness Sumire taking a bath...