The total land area of Japan is: 377,972.28 km². This figure includes 364,485km² of land mass plus inland water area such as rivers and lakes, but excludes the Northern territory which has been occupied by Russia since the end of the previous war.
The territorial seas of Japan are about 430,000 km² (l.l4 times that of the national land).
This means that Japan as a sovereign nation has an area of 807,972.28 km². This figure excludes all the disputed areas such as the Northern territories, the South Eastern Sea, and others.
Unlike nations that are surrounded by national borders on land, the size of Japan must be considered as the sum of both land and coastal area. Although the size of Japan is listed as 62th out of 257 countries as of 2015, it should really be considered to be ranked in about 30th place (i.e. 85 percentile). Japan is not a small nation at all, although the Japanese media and school textbooks repeat the statement that “Japan is a small country.”
We must also remember that many nations include massive inhabitable land such as dessert, high mountain ranges and Tundra areas. On the other hand, Japan’s coastal lands are all people friendly, with a moderate climate and an abundance of food and water.
As for the abundance of natural resources, this should be obvious just by looking at the fact that the Japanese developed metallurgy thousands of years ago, as seen in Dōtaku, ironware, and other metal ware.
Just out of interest, the following is a map of Japan in 1942.