Fan Xian didn't cross. About thirty episodes, Fan Xian opened the box left by his mother, and the letter explained why he existed in this world. His mother, Ye, came from another world and was frozen in the disaster. At the same time, another world appeared, that is, the world where Qing Guo lived, where people slowly evolved from primitive to feudal. Some people wake up unexpectedly in the frozen world, and Ye is one of them, which unexpectedly opened the door of the olive world and brought many modern civilizations to the world. Fan Xian is one of her experiments. There were many such experiments, but he survived. This experiment is to bring the memories of people in that world to this world. Therefore, Fan Xian is not crossing, but an experiment of combining people from another world with people from this world.