Mika, who divorced her husband 10 years ago, raised Tatsuya on her own. She worked hard so that Tatsuya would not feel sorry for being a single parent, and eventually he graduated from graduate school and got a job offer. As soon as she finished raising her child, she felt empty, having lost her goal. Then one day, Tatsuya invited her on a hot spring trip to thank her for sending him to graduate school. Mika and Tatsuya set off on their graduation trip just the two of them...