Back for You aka Reversing Time

When Yu Xingchen learns that his first love Su Ruo has died, he’s suddenly pulled into a time vortex that sends him fifteen years into the past. Now back in high school, he finds Su Ruo alive at eighteen. As he relives their youth, he revisits forgotten moments and uncovers hidden clues about her fate. Caught between the past and present, Yu Xingchen must solve the mystery of her death—before time runs out and he loses her forever.