[ maybe... korosensei's teacher mode doesn't have an off button, even if this girl is not his student and is, in fact, too old to be his student. Everyone can learn!! ]

Now, now, there's no need to apologize! You weren't being rude, although Sensei admires your good manners. It's nice to meet you, Mai-san.

[ he wiggles his tentacles in a manner that could be interpreted as cheerful. ]

Most people call me Korosensei, but you are free to call me something else, if you'd like.