Well my initial post said there were spoilers. And yes when they were at the point of almost being killed. He didn't piece it together until the end when it was revealed. If it wasn't for Lin it would've been over. I get this was the intent of it, but knowing of all their properties before hand and not piecing it together until Emily found them makes me say clueless and slow.
Who says he didn't? Just because he didn't blurt out "OH I KNOW YOUR SECRET!"? That's a bad idea to say to someone who might kill you. You don't even know for a fact that it is until it's proven, so you're using hindsight. If you're able to point out a specific part that could use an adjustment, let me know.
Spoiler potential:
well the reason I say that is because when he gets back to the hotel and the android is snatching around trying to grab the fairy. Once the fairy is revealed he doesn't realize she's working for the queen until she starts speaking elvish. Then he decides to talk to the other 3. The way it unfolded just made it seem like he hadn't put it together yet.
Also I think there was a typo in one of the hot spring scenes. When the MC is there with Kali's friends and he is talking to the history nut. When she's talking about her father catching free elves and the MC asks if it's common. She replies no it's not common. That 15 is a low number. If I'm reading it right I think it's supposed to say 15 is a high number but I might be misreading it. I think I made a save right before that point so I can send SS if you need to see which part I'm talking about in game.
Also I hope I didn't offend with my fairy comments. I really enjoy the game and the way things tend to work out. It was just something that didn't sit right with me but I know that's how the story is going. It was also weird that later on Sylvia knew all about the fairies beforehand and knew they were spies and were all around already and everything.