Asaka became pregnant and gave birth to her university senior's child at the age of 18. After that, her senior went missing without a trace, leaving Asaka to raise their son, Masaki, alone. Working as a nurse while watching her mother who had supported her education up to university, Masaki grew up to be an honest and well-behaved boy. Such a son was about to graduate from university and find a job. Wanting to spend the remaining little time they have together slowly, Masaki took Asaka on a hot spring trip with money he saved from his part-time job.
