Never been to Okinawa, but spent some time in the Tokyo/Yokohama megalopolis. Tokyo isn't terrible (not as bad as, say, my original hometown of Atlanta) in terms of bike-friendliness, but it isn't wonderful. I guess that many people crammed into that small of a space just doesn't leave much room for anything but mass transit. That said, the cycling community there is friendly and enthusiastic, and the drivers, being Japanese, are more polite than they are in most cities in America. Once you get out of the city, though, there are many beautiful spots in Japan, particularly if you like climbing...