Showers wash away the fleeting sunshine, and every storm is backed by gloomy weather and heavy rain. Frustration is a song accompanied by laughter in youth. Family affection, friendship and hazy love are unpredictable in the time machine. A blue letter is sent to an unknown person, filled with words to his father. It describes growth and the true feelings that have never left his mouth.
Lihuai, a girl who lost her father when she was young, looks like an ordinary person, but she remains stubbornly stubborn when it comes to emotions. She only wants to be immersed in her father's love as a child forever, remembering and missing her favorite childhood friend: Jin Yang. Faced with Wang Yuze, a classmate she met after a turning point in her life, who gave her endless care. Although she accepted this friend, she could not face Wang Yuze's love.
Many years later, when he was nearly 20 years old, Lihuai met Jin Yang again and met him day and night again. Wang Yuze was by Lihuai's side as always, and accidentally got Lihuai's blue letter. There are elusive secrets hidden between the parents, which hinder young people's interactions, university activities, and social contacts, resulting in a series of stories. There are also my best friend Lu Feishan from the university and Lin Yaer, my boss at student work. These people with colorful personalities experience the joy, success, and changes in the fleeting years.