"Remember, if you don't get true love before the age of 21, you will disappear." "What is true love?" "It's real love." "Then what is disappearance?" "Child, it means that you no longer exist in this world." The day before she turned 21, Yan Danning lay quietly on the bed, thinking of the mysterious old man she met in the street when she was five years old. She didn't know if the old man's words would be a prophecy, and she didn't know if she would be able to see the sun tomorrow. Life is like this, so be it. But when I woke up, it was already sixteen years ago...