A secret guardian angel who just so happens to be a demon... fufu, it sounds fun.

[Atsushi knows Meph is a demon, at least. So if he's ever caught creeping, he has an excuse.]

[And wow, look at this, Chuuya's so flustered he almost forgot something very, very important! Something that Mephisto would be happy to let him leave without revealing.]

[...]

[But the way he says that clearly won't let him, since it wouldn't be all that different from a lie. Heck.]

Oh? Not interested in hearing about my weaknesses anymore?