Campervan-ing Japan

Hey guys
first post today. Great forum...I cant wait to come and ski Japan

So, myself and a friend are thinking about hiring a campervan for 2 months to drive around and visit a few ski resorts this winter.

Has anyone else done this? Any tips would be much appreciated?

Are you allowed to camp in carparks or on the side of the road in Japan? specifically at ski resorts... does anyone else do this?

Also any must see destinations that are a bit out of the way would be cool.

Thanks
leeds_skier