[Calling his schoolmates by last name has transferred over pretty cleanly but- yeah, standard Japanese levels of politeness really didn't fit into America in the 2000s. Or Australia in the 1920s. That was sort of more important than figuring out if he was embarrassed to just call her Petunia or not.]

Oh. ... Can't say I've ever met someone from Australia before. [a beat]

Maybe I've met someone who was alive in 1921 but they'd be a lot older than you look. [Which is, uh, a compliment? Maybe? It's not really meant spitefully but this sure is a mind-boggling experience.]