While having a meal with his close friend, Zhuang Xiao is shocked to discover that the girlfriend he remembers being passionately in love with for a month has a blurred face, and she is nowhere to be seen even in their photos together. Mysterious text messages asking, "You really have a girlfriend?" keep appearing. He unexpectedly becomes trapped in a time loop, repeatedly returning to September 5. In the end, he breaks the cycle and reaches a happy future in which everyone survives safely.