Daoxian (Kim Jung-hyun), who was punished for fighting and participated in community service, met Xiuxian (Cai Shuchen) in the library and was deeply attracted to her. As their friendship deepened, they discovered that each other had a painful story: Daoxian's mother did not recognize her son because of Alzheimer's disease, and Xiuxian was deeply trapped in the trauma of her best friend's suicide. The two boys and girls gradually approached each other and shared their secrets and stories with each other.