What about the store? Any way to get things from other region's stores?
Login to
xbox.com with your Live account (or at least just browse the site as a guest, but login is a better idea), change the language of the site to Japanese on the top-left side, and then you can "browse" the Japanese store and see what's available. But you can only buy things that are already available in your own region. If you want to "buy" any Japan-exclusive things, create a Japanese account and use prepaid cards from PlayAsia or other sites that offer digital redeem codes (sent by e-mail).
With your Japanese account, you can access all the Japanese store contents, so you can download a free demo of the game (if it exists) and see if it works on your system before you pay for the full game. ^^