+1

This plan doesn't sound particularly well conceived. There are some scenic roads in Japan, but "north to south, stopping in all the cities" sounds like it will be mostly on very dull expressways with long stretches where there is nothing but soundproofing barrier wall to look at.

Now .... If the OP had suggested "all way way along the Japan sea coast". Or "all the way around Hokkaido", then I think that would be worth considering. Even then, I'd suggest planning the route to avoid concreted over suburbs in favor of scenic roads as much as possible.