Sun Xiaolei, a drama school student, is facing the first important competition in his life, but the delay in changing his voice makes him anxious. In the process of preparing for the competition, Xiaolei accidentally became friends with two competitors - Shi Jiahui, a boyish old girl, and Xie Tianci, who was born in a famous Beijing opera family. In the long summer, the three teenagers are about to face a "reversal" of puberty.