[He gives the surrounding area another look to confirm that there is indeed nothing (else) out of the ordinary; yep, just people milling about.]

Cos..play? Forgive my ignorance, but I know not what that is. [His assumption that it has to do with his attire is confirmed with the rest of what is said. So it's about his outfit, huh?] Non! This is merely my everyday wear. Quite stylish, don't you think?

[He's not wrong about that assumption, that's for sure... Though if Vanitas knew about such magazines, he would be on them in a heartbeat, haha... For now though, he's merely being flashy for the fish.]