David I think you should request help with planning your route first. I would be interested in hearing the forums collective advice. I only know route 1 exiting Tokyo in the opposite direction but my advice is only use in emergencies, if touring find another route.
We did it 5 years ago, with no real plan, nowhere booked to stay and only a paper map. If you follow the south coast it is pretty simple. However, highway 1 can be a bit grim, so try and get off it as much as poss.