Hi guys, I live in Fukuoka Japan. Fukuoka is on the southern main Island called Kyushu. I am not sure what the rules are but I will look into for you. My friends ride at Autopolis in Oita all the time, and in fact I may be going to get my race permit on Monday. Waiting to see what the weather will be like and if I get swamped with work.
As far as riding on the street, I think if you have a international permit with the motorcycle stamp, it should be OK. At least it was when I moved here from Canada three years ago. I have heard that finding a place to rent a bike may be difficult though, and you will only be able to ride bikes upto 400cc. My friend said he knows of a place around here where you can rent.
I think there are some free track days where you don't need your race permit, but it's not a regularily scheduled event that I know of. Basically my friends are telling me when it is OK to go and I just say sure. When are you guys planning on coming and to what cities? In the meantime I will ask a few questions and let you know.
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Les
MC21SE
CB400SF