I spoke to a friend who is fimiliar with this sort of stuff and he stated that you have to take the paperwork for the bike to the nearest off base City Hall vehicle registration. if you live on Kadena , depending on which side, you would go either the Kadena town City Hall or the Okinawa City, City Hall to register your ride, after you get the plates for the bike, you register with the base, so that you can drive on/off base.
hope this helps.
Pretty much sums it up. I just got my Ruckus the other day, I'm currently in the process of painting it, once it's done I'll be registering it appropriately.
But you need to take the bill of sale and insurance of the scooter to Okinawa City office which is right behind gate 2.. then they'll give you plates and all that good stuff. Then you have to get it "JCI" inspected (nowhere near as invasive as traditional JCI) and it's super cheap.
Anyway, myself and a friend are looking for other zoomers in the area to meet up with.