Rules World: Identity Mall

Su Chen went to the toilet and found that the people on his train looked different from those in front of the train. Since he had read many novels, he subconsciously called the system in his mind, and got a response. He also knew that he was now in the rules world. There was a mall in the system, and the rules coins in the rules world could be used to buy the identity in it. But why is this identity so expensive?