Song Cheng was a blind man.
His eyes were ghost eyes, a gift from Yune.
But what exactly were ghost eyes?
In the past, Song Cheng was unclear, but at this moment, he somewhat understood.
Ghost eyes were two "supernatural passages" connected to the source of Yune's power, hence why they repeatedly "collapsed" after Yune encountered issues and inexplicably harvested the "Human Skin Ghost's probing" at present.
The Human Skin Ghost must be the initiator of the ghost tide against Shanghe County, and its ability to bypass Yune must mean it had already surrounded her.
Now that the Human Skin Ghost's attack on Shanghe County slowed, it was highly possible it was devouring Yune, integrating with her...
During the process of devouring and integration, the Human Skin Ghost naturally became aware of this "passage."
But it merely probed, not launched an invasion.
As for the reasons...
Song Cheng speculated there were two:
