The best years are when you meet the best people, and the best years are when you meet the best friends. Because you are young, everything is beautiful, and because you are young, everything is filled with the sadness of being lost. Jiang Mumu, Yi Yalan met and got to know each other in high school in midsummer. They smiled, made promises, and worked hard for the college entrance examination together in the best years of their lives. But are those beautiful years eternal? Will those beautiful promises come true? Or will those precious memories disappear little by little as time goes by?