Mayumi became pregnant with Kota when she was 18. Her father disappeared when she found out she was pregnant, but Mayumi went against the opposition of those around her and gave birth. Mayumi raised Kota single-handedly, put her into college, and eventually she became an adult, and her child-rearing also settled down. The two of them were good friends, such as going out together on holidays, partly because she was a parent and child who were close in age. One day, Kota used her summer vacation to invite Mayumi to a hot spring trip. Kota has something he wants to tell Mayumi when she grows up, so he invited her on a trip...
