During the millennium, the story takes place in a high school in the center of Chongqing. In the fresh and simple campus and under the high-rise buildings around it, two completely different youthful atmospheres meet here. They go from being in opposition to each other and merge with each other, experiencing a passionate, silly and warm story of youth together. Here is not only the first cry of the teenagers facing the adult world, but also a warm journey of mutual support and common growth. Along the way, several teenagers with different backgrounds and personalities will face the conflict between the innocent campus and the social reality, run towards the sun in the interweaving of family affection, friendship, and ignorant love, cool as the wind and wild as a dog, and thus find a sky that belongs to them.