Iceland is the geothermal poster child, which may cause this idea, since both countries are volcanic. But Japan's population density (330/km^2) is nearly 100 ti

Iceland is the geothermal poster child, which may cause this idea, since both countries are volcanic. But Japan's population density (330/km^2) is nearly 100 times larger than Iceland's (3.6/km^2). So the intensity of geothermal extraction must be correspondingly that much higher, which turns out to be impractical.