[he doesn't MIND talking about himself, usually. Just never thinks to do so. And well... Akechi knowing about him on a deeper level is Appealing]

I'll do both since I don't think you're going to like the second answer.

[He finishes his cup and tosses it in the trash]

We didn't start until you confronted us at the festival. Me and Mona both noticed way back at the tv studio but we didn't connect you to the Black Mask until much later. We didn't have any reason to suspect you at the time. In hindsight, it feels obvious, but...

[Sorry Akechi, it wasn't some months long plot]