South Australia (Australia) is 2.6 times larger than Japan.
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
South Australia is a state in the southern central part of Australia. It covers some of the most arid parts of the continent. With a total land area of 983,482 square kilometres, it is the fourth largest of Australia's states and territories. Wikipedia