Because, Yang Chen had already left the Western 42 Regions, and followed the Northern Territory Sect to the Central Region!
The Northern Territory Sect was not from the Western 42 Regions, so they declined the invitations from the various forces of the Western 42 Regions and did not participate in this grand event. As Yang Chen was a member of the Northern Territory Sect, it was natural that he did not participate when his sect did not.
When the Northern Territory Sect returned to the Central Region, Yang Chen left with them.
Upon leaving, Yang Chen left many letters. These letters were all written by Yang Chen himself and were given to different people, so that things could be properly arranged after his departure.
For example, letters for the Jinling Holy Girl and those for the Luosheng Gate, and so on.
This way, the people who had helped him would not feel that his departure was too sudden, and he also revealed his identity to them.
