We went here last year and it is AWESOME Massive range of parts in stock, mainly appearance items and bracing. By Japanese standards the amount of stuff on display is huge.
Lots of KG Works, Nakamae and Zoom Eng, Mazdaspeed items were some hardware (clutch) and a lot of trinkets (mugs, keychains etc). Good range of Carbing pieces too. Prices are catalog, and they didn't shave off much for a cash discount.
It's about an hour's ride north of central Tokyo, easy to get to by train, and it's a 5min cab ride from the closest train station....if you buy enough stuff, they will drive you back to the station in the shop van and as you leave the entire staff comes out to bow