The story begins in 1995. The male protagonist and his grandmother moved upstairs to the female protagonist "Ponytail" "that day", when both parties were only 15 years old. That day, he was a man from a poor family, with a withdrawn personality, a broken right hand, and a talent for painting. However, he decided not to go to school because he couldn't stand the cynicism of his classmates. The heroine "Ponytail" is a person with an average family background, cheerful personality, kind heart, and great writing talent. The two of them obviously lived upstairs and downstairs, but they communicated by writing letters. "Ponytail" gradually opened "that day"'s heart, and the two became good friends. Ponytail would tell a story to that day when he came home from school every day, and he would draw a picture to that day every day. Later, Ponytail discovered that he had a talent for writing, and began to concentrate on writing. Every time he wrote a story, he drew illustrations for him that day. Just when the two were getting along well, Ponytail's parents divorced, Ponytail followed his father, and they decided to move to another city. Ponytail and that day kept in touch by writing letters. Suddenly one day, Ponytail never replied to her letter, and that day began to look for her like crazy...