Sumire, the wife, is under pressure from her mother-in-law to give birth to a grandchild, and is ordered not to have sex until she goes on a hot spring trip in a month's time in order to have a baby. However, on the day of her trip, her husband unexpectedly refuses to have sex with her. Meanwhile, her father-in-law also tries to hold his wife, but is also refused. The two, overcome with sexual desire, headed to a hot spring to soothe their aching bodies. Then, her father-in-law, who happened to witness Sumire's sexy bathing appearance, was unable to suppress her desire...