Junya, who lost his mother a few years ago, lives with his father in a three-legged race. His father brought Mayu, his remarried partner, to him at the end of the summer when Junya was preparing to take the exam. For Junya, life with Mayu, who is too young to call her mother, is a series of confusions and temptations. It is inevitable that a young man who has just entered adolescence will suddenly appear and realize that his young mother-in-law is a woman.