So I'm reading Heir to the Dragon finally after all these years. Love it so far and I don't know why it only took me 18 years or so to get to it.
But there is one issue I have---it feels like the Japanese language usage was taking from anime or something. It's not realistic.
For example, in the beginning of the novel Takashi Kurita says "wakarimasu ka?" ("do you understand?") to his six year old son (later in the novel, this word is misspelled wakarimas). An odd thing to say to one's own child, as this form of the verb is distal---it's what you would say to a stranger or a business partner or your boss, while one would speak in the direct style ("wakaru?") to one's own son. But Takashi is precisely the kind of person who would talk in the distal style to his own son---so I think it works great. But later, Takashi says to his now adult son so ka ("I see," "oh, really?"), which is direct style and familiar (rather than "soo desu ka," the distal style and the same style he used when he addressed his son as a six year old). In fact, every time anyone says the phrase, it comes out as "so ka"---regardless of the circumstances---when "soo desu ka" probably would have been more appropriate. On a similar note, I think the distance in the relationship between Theodore and Takashi would have been shown had Theodore said "domo arigato gozaimasu" when Takashi "congratulated" him upon his graduation, rather than the direct style and less-formal "domo arigato."
I've also noticed that every time someone says "yes," regardless of the circumstances or who they're talking to, it's "hai," but in most circumstances this is said, it would have been more appropriate to say "ha" ("yes, sir").
And outside of anime, I don't think most people call other adults with the suffixes "-kun" or "-chan," unless the two are very young adults or very close---otherwise it's demeaning.
Phew. Sorry: it's sorta like watching a lawyer TV show where they get everything wrong. I really can't complain, though, because I think the novel is outstanding. And I reckon these issues I raise don't matter to the vast majority of readers (because y'all don't speak Japanese).