Sumire raised Kotaro desperately as a single mother. Thanks to her desperate efforts, Kotaro safely graduated from university and got a job. As Kotaro began living alone, Sumire reflected on her life. It was a joy to see Kotaro grow up so well, but what about her own life? One day, Kotaro invited Sumire to a hot spring trip. The trip begins with Sumire, who is troubled about her own life, and the optimistic Kotaro, who doesn't care about his father.
