Please Explain

Ryu didn't seem to be surprised by the sudden voice at all. He had spoken these words for himself, but the ears of cultivators were sharp. On top of that, there were very few things that could hide from Ryu's [Third Perspective]. 

After spending so long chasing this 'assassin', Ryu had deployed his sharpest senses long ago. Even this woman wasn't able to hide from him, even though Ryu could tell that she had actually stepped beyond the World Sea Realm. 

This wasn't too surprising, though.