What Does It Mean That I Traveled Through Time and Became Someone Else's System?

Ye Lin was sexually harassed by her partner's boss at work, so she resisted and slapped him in the face many times. While trying to save a drowning person, he accidentally died. When he was about to die, he accepted a rescue mission in a different world, just so that he could be resurrected and return to his original world. Countdown to doomsday, zombie outbreak, country destruction and family destruction, zombie siege... Lan Feng: "We all said the end was coming, but no one listened to me, and they almost put me in a mental hospital." Ye Lin: "Congratulations on activating the Tiandao Reincarnation System. I will be your guarantee in the end." Lan Feng: "What? System? Could it be that just like the system novels I read, I also have a golden finger?" Ye Lin: "Well, almost." Lan Feng: "What do you mean almost?" Ye Lin: "It literally means, whoever believes in me will live." Lan Feng burst into tears: "Believe, I believe it too much." Then he turned around and said, "I will become the most beautiful boy in the world."