Japan is 77% larger than Idaho (USA).
Area: 377,915 km2 World Factbook
Population: 127,103,388 (July 2014) World Factbook
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south. Wikipedia
Idaho is a state in the northwestern region of the United States. Idaho is the 14th largest, the 39th most populous, and the 7th least densely populated of the 50 United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Wikipedia