The game itself is also created to be English letters only as well, so unfortunately any foreign keys (even the pound symbol on UK keyboards) will cause the game to crash. Due to that you wouldn't be able to use such things like hiragana or kanji, since specialized letters and languages are not inputted to work with the game, but you are able to use the English-ized versions of words as long as they're appropriate in the rules with what Vortex linked.