There is a site out that for Foreigners in Japan and riding motorcycling. Google for it. You're in for a whole new world!
Found it: it's gaijinriders.com (gaijin is a foriegner, I think sometimes derogatory).
Bottom line: imports are subject to up to 100% duty and anything over 400cc requires the top tier license; my U.S. license only converts to a mid-level license.
I will sell the Ninja 250 and VStrom 650 before I move, then look for a unique (non-U.S.) model when I get settled.
Maybe this XR250 Motard for my daily Tokyo commute?