Greetings!
These are excellent questions! Unfortunately, as far as I can tell, they are not addressed in the APA manual. The safest thing to do would be to ask your instructor. If you can't do that, logic would suggest that, unless you know that your reader speaks (reads) Japanese, there is little point in quoting it in the original Japanese. If the work has ever been translated into English, you would, ideally, use the translated version. Otherwise, if you are translating it yourself, you could simply say, in your parenthetical citation, (trans. by author). I can't say that this is standard, but as the APA manual does not answer this question, I think that's the best solution.
Best of luck in your studies!
Thanks,
Sarah, EssayForum.com
Sarah, EssayForum.com