Every city has gaps.
The convenience store at three in the morning, the elevator that never stops on the 17th floor, and the bus stop that only appears when it rains.
People passed by it countless times and never noticed it - until Jiang Yuan heard a rule that shouldn't exist.
There are three rules written on the wall. Others can only see the surface, but he can hear the echo - vague, like a whisper coming from the wall, telling him what is hidden behind the rules.
Echo says: Rules are not just rules, they are puzzles.
His name is Jiang Yuan, and he heard the secret rules.
