Hibiki, who raised her son alone, once had a relationship with her son who took care of her when she collapsed from overwork, finding a trace of her husband in him. Now, three years have passed without incident, and Hibiki begins to consider remarriage. While hoping to return to a happy life with her son and her new husband, she also feels remorse for the mistake she made three years ago. In order to sort out her feelings, Hibiki decides to go on a hot spring trip with her son.