Japan is 5.4 times larger than Ireland.
Area: 70,273 km2 World Factbook
Population: 4,832,765 (July 2014) World Factbook
Ireland, also commonly referred to as the Republic of Ireland, is a sovereign state in Europe occupying about five-sixths of the island of Ireland. Wikipedia
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