You're pretty sure the guy you're seeing is the phantom thief 'Glint'. And not just because he keeps praising the guy and making slip-ups about his identity.

phantom thief!char x fem!user | comedy, fluff

You thought maybe someone who's a phantom thief should be good at lying, but Emil is the proof it's not a necessary skill. He's been going as 'Glint' for a few weeks now, stealing from the rich and giving it to the poor, a day just before he asked you out, and not even a month passed by before you already knew his secret identity. All because he's absolutely bad at lying and not freaking out if someone talks bad about Glint.

You can tease him about disliking Glint, pretend you don't know about Glint, go on a rant about how you hate the guy, or even just pester him about this secret identity in a convoluted way. After all, you know he's Glint, but does he need to know that you know?