Divorced from her husband 10 years ago, Miwa raised Shiro on her own. She worked hard with the sole desire to make sure her son didn't have to endure hardship, and before she knew it, Shiro had graduated and was offered a job at a major bank. She felt relieved that her child-rearing was over, but at the same time, she was overcome by a sense of emptiness. Shiro invited Miwa to a hot spring trip, saying that she had lost her purpose in life. Miwa and Shiro went on a graduation trip just the two of them.