Ms. vs Buddy

Lei: So your teacher's name is XX.
Ya: No, Ms. XX.
Lei, OK, so what do they call you, Ms. Cynthia?
Ya: Yeah, when you call a girl or woman, it is Ms. plus their name.
Lei: How about boys? You also call them Ms. ZZ?
Ya: No, you can not do that.
Lei: So how does your teacher call **(a boy in Yaya's class)?
Ya: (thinking for a little while), buddy, you call a man or a boy "buddy".
Lei: (smiling) Oh, yeah?