Masaaki had lived alone with his father since childhood, knowing his mother, Ema, only as a gentle and beautiful figure in his memories. On his 25th birthday, he received a letter from her containing the words, "I want to see you again after 20 years," and Masaaki decided to answer her call. The reunion took place at a hot spring resort the family of three had once visited together. There, Masaaki begins to realize that his feelings for his mother are transforming into romantic desire.