If it was a spell coming toward him, then the flying humanoid demon might have been able to sense the nether coming at him.
However, now that the caster himself used its body as a cannonball, it took the flying humanoid demon a second longer to notice Blake that was already a few meters away from crashing into him.
Blake had used the combination of both his wings and the single darkness tendril to launch himself forward, straight to the flying humanoid demon's body.
Blake thought that fighting the flying humanoid demon was dangerous considering he didn't know about any capabilities of the humanoid demon from the second realm.