Every day at 3:13 in the morning, Qichuan forgets something.
It could be a street, a building, a piece of history, or it could be a person.
Late one night, Jiang Ci, a restorer of old objects, suddenly discovered that his ID card was invalid, his files were cleared, and there were no images in the surveillance. Even his biological mother answered the phone and asked him who he was.
In order not to be completely erased from the world, he boarded a subway that did not exist on the map - Line 13.
At the end of the train, he met his sister Jiang Li, who disappeared seven years ago but remained twelve years old forever.
But she told Jiang Ci:
"Brother, I'm not missing."
"It was me who took the initiative to make the whole city forget about me."
Behind the reality lies a "remnant city" composed of missing people, wrong history and abandoned future.
Every time a forgotten person is rescued, another person may disappear from reality; every time Jiang Ci borrows the future, the person Jiang Ci cares about most will lose a piece of his memory.
When the whole city begins to forget him, Jiang Ci must choose between seven million people and his sister.
But he gradually discovered that thirteen years later, he had already chosen for him once.
