After divorcing her husband, Touko raised Yuki on her own. She worked hard so that Yuki would not have to endure such hardships, and even after he entered university, she worked hard to pay for his tuition. When Yuki got a job, she began to feel a sense of emptiness as her child-rearing came to an end. Then, Yuki invited her on a trip to a hot spring, and the two of them set off on their graduation trip together.