Not sure if this is the right place to post this or not, but just for my own personal edification/entertainment as an old school import gamer I created a site to track some of the Japan only games/apps on the app store from the more notable developers who also have a presence in the West (ie. Konami, Sega, Capcom, etc) since Appshopper, etc doesn't seem to track games that don't exist in the US app store, so in case anyone here is interested as well, I thought I would pass along the web site. I will probably build it out a little more in the next few weeks, but it is basically functional and should update with new games and price changes as they occur daily. If you don't have a Japan iTunes account you can google and find some tutorials on how to set one up without a credit card (so you can download free games at least).
Anyway, the site is here - http://www.nihonappworld.com/
, if anyone is interested in checking it out.
Also, in case anyone is wondering, the iTunes IDs for a lot of the US and Japan games are different for the same applications (ie. Final Fantasy IV will have a different ID in each store), so there isn't really a sure fire way to determine which games do or don't exist in both app stores, so I am just tracking some of the major developers for all of their games available in Japan, so there will be a lot in there that exist in the US as well (but there are also a lot that do not exist at all).
Mods, feel free to move this if necessary if I am posting in the wrong place.