A single-mothered girl asks an acquaintance to introduce her mother to a man, and the man suggests a trip to a hot spring. The daughter is relieved to see that her mother likes the middle-aged man the man brings, but as she endures the man's sexual demands for her mother's sake, she gradually becomes aroused. When the four of them take a bath together, the mother becomes aroused by seeing the daughter's actions. Eventually, the mother, daughter, and the two men engage in an orgy.