AWD is one small tool in your winter motorists toolkit. The most important tool is the one sitting in the drivers seat. Having AWD does not prevent flat tires or other mechanical failures that could leave you stranded in life threatening weather. Additionally, AWD does not prevent you from getting stuck. Slide off a snowy road into the gutter and, chances are you will be stuck so well that AWD will not even come close to getting you out.
The bottom line is, when driving in remote areas, it is irresponsible to depend 100% on your vehicle (even if that vehicle is a Unimog). Whether on motorcycle or car, in remote areas, snow or desert heat, I am always prepared to survive at least a few days. In extreme winter this entails a little food and water and a mummy bag. In the summer heat it entails drinking water and sun protection.
I'm surprised Japan still has areas where one couldn't summon help via cell phone (although the American West still has vast areas without service). Even with cellphone service I would have minimum survival gear in the event the service is not useable. Do NOT rely on AWD to keep you alive. It's a very small advantage and, with the capabilities of most modern FWD drive cars, I would not consider AWD mandatory, even in N. Japan. I do hope you run full-on snow tires (AWD or not).
