That day four years ago, we only made it once... Since her husband died eight years ago, Kiyoka has been living with her only son. As the time for her to leave her son, who is moving far away for work, draws near, memories from four years ago come back to her. When she asked her son what he wanted to do to celebrate his college entrance, he asked for sex, and they ended up having sex just once. The hot spring resort makes Kiyoka let go of her everyday rationality, and in this extraordinary environment, she unleashes her sexual instincts. And today, she makes the same mistake again...