I guess here's where a Chinese GCSE comes into use...
I translated the Kanji characters in Kurogane's dialogue:


Kanji is a Japanese character form based on Chinese, and since Kurogane uses only Kanji in this dialogue, he could be speaking either. However, because of the culture of his country (Tsukiyomi, Amaterasu, etc.) and the fact that he uses a Japanese sword, I'd say it's Japan.
Also, Fai uses Russian characters. Though I could not find a translation for his dialogue, I can say that all characters he speaks are in modern Russian. No outdated characters could be found.
Edit:
Okay, not sure if this only applies to my computer, but all Photobucket images are not showing. I'll give a text translation instead. Kurogane firstly asks about travel/carrying to an island by flight, then the next page, he talks about a path to Hanshin Castle.