It's the beginning of the first year of high school, and it's August in City A. It's sunny or rainy.
In the corridor of the Chushui Middle School, a reckless girl Lin Fu knocked over the exercise book in the arms of a young boy Jiang Yichen. An unexpected collision caused the two people who were originally parallel to intersect. She was panicked and blushing, like a frightened little rabbit; he was calm and restrained, but his heart beat wildly when their fingertips touched.
Later, Lin Fu's best friend Wen Ruoyun and Jiang Yichen's brother Xu Yi also entered each other's world. The four of them went crazy together, laughed together, got into trouble together, and grew up together, making the three years of high school the most vivid life.
From strangeness to familiarity, from walking alone to someone else under the umbrella - this is a story about youth, friendship and heartbeat, and a journey of youth that starts on a rainy day and ends on a sunny day.
Concept: Chushui F4's growth and love story