The incident involving the Death Prison Forbidden Land and the Yun Ci Guild happened within just half a day of each other, and there were quite a few connections between the two under the surface. The fact that both were eradicated completely makes it hard to believe that it was merely a coincidence.
Moreover, although all the people in the ancient castle were killed by Ning Fan that night, there were quite a few prisoners in the Death Prison Forbidden Land who saw Ning Fan's face and then left. It's uncertain whether someone linked these two events and then found those prisoners to get a description of Ning Fan's appearance.
"As expected, no plan is foolproof…" Ning Fan said with a bitter smile.
As for the identity of Phantom Asura, Ning Fan had kept it well-hidden for years. If it hadn't been for his decision to take revenge for Ouyang Feifei and wipe out the headquarters of the Yun Ci Guild, the world might have thought that Asura had disappeared forever.