Three years ago, Sayuri divorced her husband and lost custody of her son, Kohei. Desperate not to be separated from him, on the night before leaving the family home, she became physically intimate with Kohei. Since then, allowed to see him only once a year, their reunion has become the sole purpose of her existence. This year, Kohei's father remarried, giving him a stepmother. This news filled Sayuri with anxiety, fearing Kohei might be taken away by his new stepmother. Now, the day of their first reunion since the remarriage has finally arrived.