This nice summary at a global level by Adair Turner notes that there is plenty of room for solar and wind power in most countries AND a low enough cost that "within 20 years many countries could get a majority of their electricity from renewable sources at an easily affordable price." He notes that in a few countries with high population density (e.g. India, Bangladesh, S. Korea) we may need to add some nuclear and carbon recapture technologies to make a swift transition to a zero carbon economy. And some rich countries (Britain) may prefer to pay a bit more for electricity to place their wind farms offshore, for aesthetic reasons.
Japan (and Germany) are absent from the analysis. Japan's population density (336 persons per square kilometer) is lower than S. Korea (507), India (407), Taiwan (647), Bangladesh (1119) and similar. But like Britain Japan has a strong "NIMBY" tradition that allows localities to veto many types of developments. So site availability will continue to be an issue for renewables in Japan.
Some ways around the issue:
Solar -- as much rooftop and BIPV as possible, on every new house and commercial or industrial structure! Floating solar on ponds, reservoirs, etc. Solar greenhouses.
Wind -- offshore with floating projects as they become commercially viable, and massive new capacity additions in Tohoku and Hokkaido with sufficient transmission capacity to get the power to demand centers in Kanto (and Kansai).