When Maki was 18 years old, she became pregnant and gave birth to Tatsumei. - His father disappeared, and Maki single-handedly raised Tatsumei and even enrolled him in college. - Since they were close in age, they were close, going shopping and traveling together, and were more like friends than parent and child. - One day, Tatsuaki took advantage of winter vacation and invited Maki to a hot spring. - Maki was looking forward to the trip as usual. - However, Tatsuaki had something he wanted to tell Maki when he became an adult, so he invited her on a trip...