1948 In the middle of winter, a man received a thick letter on his birthday on April1. This letter comes from a dying woman and tells a touching love story, but the hero of this story knows nothing about it. The story began 18 years ago: a girl fell in love with the writer who lived next door when 13 years old. The little girl moved to another place because of family changes, but she never forgot the writer who once lived next door. A few years later, the little girl returned to her original residence as a student, reunited with the writer and dedicated her first night to him, but the writer had no impression of the little girl who once lived next door. After they had sex several times, the screenwriter left because of something, saying that she would contact her as soon as she came back, but there was no news from then on. The girl found herself pregnant in a desperate wait. Because of her love for the writer, she decided to give birth to the child. Life became more and more difficult after the baby was born. In order to let children live a superior life, girls have to rely on the rich and live a prostitute-like life. A few years later, she finally met the writer who had loved her for many years again. They had another happy evening, but the writer still didn't recognize her. A few years later, the child died of illness, and the girl wrote the past in a letter and sent it to the writer.