A thing you kinda have to drive there in person to understand about narrow mountain roads in Japan, is that they have a ditch for water runoff on one or both sides. It’s about a foot deep and a foot wide and completely square. Often they’re covered with gratings or tiles, but often they are uncovered. And they will absolutely eat your wheel if you get in one.
Like auto insurance carriers have a whole special section about roadside assistance specifically for pulling you out of those roadside gutters