Aki and her husband divorced, and their son lived with his father. The day before they left home, Aki was so lonely that she had a relationship with her son Naoya. After that, once a year, only the day when I could meet Naoya was worth living. Eventually Naoya's father remarried, and Aki wasn't worried that Naoya would be taken by her mother-in-law. The day has come to meet Naoya for the first time since she had a mother-in-law ...