Nero studied Vanessa's expression and body language to get a peek into her thoughts, or at least intentions, but she had learned to mask them well. By keeping a completely neutral face, and her body in its natural stance, she prevented him from gaining any insight. But just as with the previous team of Neophytes, purposefully maintaining neutrality was all but admitting that they were trying to hide something from him.
When she asked him how he found her, Nero was tempted to not tell her. It was genuinely getting harder and harder to spot her, and he was not blindly arrogant enough to think he'd always be ahead of her if she kept making progress at this rate. But he told her anyway.
While she could grow from his guidance, only a real challenge would help him grow. Hesitation and fear would slow down his path, so he just mentally prepared himself to be even more aware of his surroundings than before. In fact, he might invest in a card that augmented his perception.
