Japan is 3.8 times larger than Korea (South).
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
Area: 99,720 km2 World Factbook
Population: 49,039,986 (July 2014) World Factbook
South Korea, officially the Republic of Korea, is a country in East Asia, constituting the southern part of the Korean Peninsula. The name Korea is derived from Goryeo (also spelt Koryo), a dynasty which ruled in the Middle Ages. Wikipedia