So I guess I really don't know that much about Japanese imports for the Dreamcast, save for those shumps that you can play without knowing how to speak Japanese.
There is some "interesting" stuff out there. For example check out this Ebay auction:
Yeah... It's a dating sim type game for Neo Genesis Evangelion! With a custom dreamcast mouse even! Games like this just make me scratch my head in confusion.
So I guess there is alot of dreamcast stuff out there that I may never know about. For now I think I will focus on the US and Europeans releases though. If I ever get into Japanese imports it will be after my North American/European collection is complete...