Arisa, who divorced her husband 10 years ago, raised her son, Yuki, on her own. She worked hard so that her son would not have to endure such hardships, and worked hard to pay for his tuition. Thanks to her efforts, Yuki managed to graduate and find a job. Just as she was feeling lonely after raising her child, Yuki invited her on a trip to a hot spring. The two of them set off on a graduation trip just for mother and son.