City A, winter, physics volume, that's the beginning of the story.
Song Yi & Xu Qing (running in both directions)
Song Yi: "I just said your name a few times, and you took up my entire youth."
Xu Qing "People change, forget about me."
There will be regrets in life, and we must move forward with regrets.
Purpose: Everyone has his own life trajectory, and we must make the right choice.