Nina has been raising her son on her own. Her son has gotten a job and she encourages him to live alone, but he refuses to go out. She invites him on a trip to a hot spring for a change. During the trip, he suddenly confesses his feelings... he says he's always loved his mother, even though he never had a girlfriend. As her son confesses his feelings for her since he was little, Nina gradually begins to take him seriously. She feels sorry for her son, who is still a virgin because of her... and she only intended it to be a little maternal love... It was only supposed to be a one-time promise, but the mother moans in pleasure. A forbidden mother-son incest story that continues to unfold.