> Also, is not the population density fairly high? There's not as much land to spread in low-density car centric suburbs like there is in (say) the US.

LOL no. Outside of the big neighborhoods of the big cities, Japan is endless urban sprawl. I know because I live in a small Japanese city of 40k people and it's just detached houses, small 2-story apartment buildings, a big box stores. Public transportation is almost non-existant and I need to drive my car everyday for everything.