Anzu in her second year referred to everyone by first name quite flatly ( unless they were older than her or seemed stricter/less close to her ) because she was used to that in her old school where everyone is also a girl, so she was simply more aware of that but now in ES, she refers to everyone as their last name with the san honorific to it to be more formal.
Unless they're not working in which case she'll go back to normal.










