In the rural towns, houses can be bigger if they are older, but modern design in Japan builds small houses right next to each other and it is easier to build a small tight suburb because of the way infrastructure and land ownership works. So like you'll see a small cluster of a dozen houses all right next to each other in the middle of farm fields.

There’s definitely an aspect of suburbia - eg a lot of Hachioji, although the zoning is a bit different and that’s shaped the way they’ve emerged. It reminds be a bit of the way London has expanded - suburban areas centred on stations of train lines that were laid out in the 60s, with low-rise houses that are larger with modest outdoor areas. Tokyo proper is also smaller than the Tokyo conurbation that includes parts of Kanagawa, Chiba and Saitama prefectures, where the density really starts to fall off and give way to agriculture.

I am not a Japan expert, but my understanding is that houses are generally smaller across the country, because land has always come at a premium due to higher population densities.