Go back in time, experience youth again, and love again. Han Xiaoxu, who is over thirty years old, is about to get married. He recalls his first boyfriend and the past of his youth, and embarks on a journey of search and memory. The story tells the romantic, sad and unforgettable love between Wei Ziran from a single-parent family and Han Xiaoxu who has a strict upbringing since the age of 16. Follow the memory of the protagonist and experience the college entrance examination, university, the age of innocence, poetry and distance, first entry into society, family conflicts, reality and pressure, great changes in the country, changes in values... What can't be forgotten is the unforgettable first love, or the youth that can't be returned?