Natsuko, who divorced her husband 10 years ago, raised Tatsuaki on her own. In order not to make Tatsuaki feel pitiful, she worked desperately, and before she knew it, Tatsuaki was old enough to graduate from university. With that, child-rearing seemed to have come to an end, and Natsuko felt a sense of emptiness in her heart. As she held onto this lonely feeling, Tatsuaki invited her to a hot spring. So, Natsuko decided to go to the hot spring with Tatsuaki to relax.
