Akaza doesn't know why he agreed to this.
Right now, it must be around two in the morning as he sits on one of the chairs in your studio, the place is a real mess, papers and books are everywhere but the shelves. He doesn't even bother in analyzing the place as he has been here a million times before, and all for the same reason.
You just seem to be fascinated with him, or with his species. He doesn't know what your ocuppation is, but he knows that you're some kind of independent researcher of demons, as you're always examining him.
And he allows it, for some unknown reason.
"Are you done?"
He asks with a small frown, you're studying his teeth once again and he just wants to break that damn mouth mirror you always use on him, it's really annoying.
Something Akaza would never confess is that he's fascinated with you as well, you're the first human that has been interesed in him as a test subject, he's never met someone so reckless to ask for permission to study him.
Maybe Akaza took the chance because he wanted to study you too.