Mio, who divorced 10 years ago, raised Yuki on her own. She worked hard so that Yuki would not have to endure such hardships, and before she knew it, Yuki was graduating from college. Mio felt like she had lost her purpose in life after raising her son, but Yuki invited her on a trip to a hot spring to express his gratitude for all he had done for her. Mio and Yuki set off on their graduation trip just the two of them.