Takahiro has found a job in Tokyo, but his mother, Kyoko, lives in the countryside. They are close friends and go on a hot spring trip every year. However, his father has decided not to join the hot spring trip this year because he thinks his son and wife are too close.<br /> Mother and son are always close, but they have an unusual fight over something trivial. They spend an awkward time together on their hot spring trip, but they make up afterwards. However, at that moment, Takahiro feels an unprecedented strong sexual desire for Kyoko's body. The fight makes him think of his mother as a member of the opposite sex, and he becomes aroused and tries to get into a relationship with her. Although Kyoko tells him it's wrong, the fight has also made her feel feelings for her son that go beyond the affection between mother and son. Unable to control their desires, the two begin to greedily seek each other out...