Japan is an island country in East Asia located in the northwest Pacific Ocean. It is bordered by the Sea of Japan to the west and extends from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south. Part of the Pacific Ring of Fire, Japan comprises an archipelago of 6852 islands covering 377,975 square kilometers (145,937 sq mi); the country's five main islands, from north to south, are Hokkaido, Honshu, Shikoku, Kyushu, and Okinawa.

South Korea, officially the Republic of Korea, is a country in East Asia, constituting the southern part of the Korean Peninsula, and sharing a land border with North Korea. 25 million people, around half of the country's population of more than 51 million people, live in the Seoul Capital Area, the fifth-largest metropolitan area in the world.