Ten-year-old girl Li Shan (Choi Soo-young) was isolated and excluded by a group of girls led by the girl Bora (Lee Soo-in) at school because of her poor family background. On the day before summer vacation, Li Shan met Han Zhiya (Xue Hui), a girl who was about to transfer to the school in the new semester, in the school corridor after school. Although the two girls had just met, they quickly became good friends. Li Shan even invited Han Zhiya to live in her home. Han Zhiya and her grandmother lived a life of dependence on each other. The two lived in a luxurious big house. Although they had plenty of pocket money and fashionable mobile phones, Han Zhiya obviously did not enjoy this lonely life. The days of running in the streets and alleys with Li Shan became her best memories. However, it didn't take long for the friendship between the two girls to have a slight crack, which became more and more intense after Han Zhiya met Bora. On the first day of the new semester, when Han Zhiya ignored Li Shan's greeting, the precious thing in Li Shan's heart was shattered.