Also, don't forget the Ainu.
they're not real people anyway
/20thcenturyjapan
I did forget them, though. It's pretty easy, my mistake.
Well, saying 'everything's been weeded out into dialects' is just such a curious expression. Languages are...uh, kind of oppressive? (You can get a creole or a pidgin but... Everyone 'knows' the language is specifically invented since it exists alongside its parent languages within living memory, so it's not that things have been weeded out so much as they were blended, and there's the recognition of the language's origins and of groups that
specifically don't speak it.) Languages are 'oppressive' because they're the original shibboleth. You know, very obviously, exactly who is like and who is not like you. You need a word for that. So you don't get a situation where Chuichi doesn't know what to call the in-group IRL. This can maybe be justified by the specific in-group identifiers only existing in contact zones, but that's exactly the sort of thing that would pop up in a 'what you neeeeeeed to know to fit in' on a Ninja Info Card for the area.
I say Chuichi is backwards because, well, take China. That's an area where pretty much everyone knows one language in common, has common cultural heritage, and they have, if anything, a heightened sense of their ethnicities and differences. There's lots of 'varieties' of Chinese but they're not always intelligible. Most of them aren't. There's dots and outposts in a sea of Mandarin-speaking Han, because Mandarin has been imposed on top of the other varieties. But you ask anyone if they're from Qingtian or Guangzhou or if they're Hakka or Miao or whatever and they'll assert exactly which area of 'China' they're from, exactly which division they belong to, and exactly which version of 'Chinese' they speak.
Or maybe you object to that example because China is a unified state with the ability
to impose language. Then take the various Turkic languages instead. Very very roughly, everyone understands the people near them but they start having trouble further away. Uyghurs understand Uzbeks and Kazakhs understand Kyrgyz(es?) but introduce someone speaking Istanbul Turkish to any one of those four groups and they'd have trouble making out what the other means. It's more of a continuum of intelligibility across many states but one of the most important things in the area was always your 'people', knowing exactly who you and your ancestors were.
Or European language before the rise of unified dominant Academies or nationalism—there's jokes about Brits not understanding each other even today, and they haven't had a migration in a few hundred years. There's still Plattdeutsch and Walloons and, I mean, Catalonia ought to be enough to put to rest the idea that groups spending time together will create a unified super-group. Spain's been a single state for hundreds of years and still has immense divisions in region, language, and cultural identity.
Meanwhile Boruto's Dad-land is multiple different countries all speaking roughly the same language with dialectical differences. Sure. By my understanding of language, the fact that there's mutual intelligibility means that there's not just common history but a common origin. That's reinforced by the hard wall of non-intelligible ethnic groups like the, what are they called, the Anchikar? Then Chuichi configures language as...like, a river, instead of a tree. It's backwards. They differentiate, not join. The fact that the language doesn't even name itself sort of posits the idea that they're the only possible group, when that's clearly wrong.
I mean. He's a character, and I'm pretty sure that ninja aren't exactly educated in the same subjects that a university student is. And it is interesting, in a weird 'this character has a strange, probably incorrect, perspective' sort of way.
Uh. This was rambley and not entirely on topic.