I'm a bit worried about this too. We're going to be driving from Jomokogen Station to Gunma, through the Teriha Valley by Tone River and Lake Akaya. Then from Gunma to Yamanouchi the next day; driving around the Nagano foothills, Matsumoto, and eventually crossing into Gifu via the Tateyama Kurobe Scenic Alpine Route between Toyama and Shimano-Omachi. We'll be taking the rental into Ishikawa and Kanazawa for a few days, and then finally returning it in Kyoto. We're relying entirely on English GPS for the trip and hoping that we'll be able to navigate the roads and signs. JTB is facilitating the rental for us through a local company, possibly Toyota. I assume I'll need to get an international driver's license at some point before our trip. I've never driven on the left side of the road before and I'm not really looking forward to it!