Here's one that I didn't see mentioned...but when they offer their hand for a handshake, don't be a limp fish. Take their hand and give a good grip (not one that will crush their hand but have it be strong enough to show them your confidence).
Other things that I can think of:
Dress nicely. A dress shirt would be great. But don't over dress. No spills or stains on the shirt, make sure things are ironed or at least not wrinkly.
Have good hygiene. Make sure you brushed your teeth, took a shower that morning, your hair is kept and trimmed and so on.
Be confident. You're pretty much selling yourself to this company. Although you may not think highly of yourself (not saying you do or don't lol), give that smile and sell yourself the best way you can.
Eye contact. I'm not sure if this will be the best thing to do in Japan, but most likely it will be. It tells the interviewer that you are confident and that you are attentive. This will definitely help.
Make sure your resume is up to date and that you're not lying on it. Lol. You've got to be honest but make sure you sell your best qualities and present it well on paper.
Other than that, I think everything else has been mentioned. Good luck on your interview. You'll do great. :thumb: