Mayumi became pregnant with Kota at the age of 18. The father disappeared when he knew that he was pregnant, but Mayumi overwhelmed the opposition and gave birth. Mayumi raised Kota by herself, entered the university, and eventually became an adult, and even after raising her child, she settled down. Partly because of their parents and children who are close in age, the two were close friends, such as going out together on holidays. One day, Kota used his summer vacation to invite Mayumi to a hot spring trip. Kota had something to tell Mayumi when he was an adult, so he invited him to travel ...