Since her son lost his father at a young age, Mai has been living with her son. Her son, whom she raised with care, grew up healthily without any rebellious phase, graduated from university, and secured a job. However, when she found out that he would be assigned to the Kansai region, she became anxious. Now, her son had become more than just a son to her. Mai invited her son on a trip to a hot spring to make a last memory together.