Japan (Japanese: , Nippon or Nihon, and formally ) is an island country in East Asia, located in the northwest Pacific Ocean. It is bordered on the west by the Sea of Japan, and extends from the Sea of Okhotsk in the north toward the East China Sea and Taiwan in the south. Part of the Ring of Fire, Japan spans an archipelago of 6852 islands covering 377, 975 square kilometers (145, 937 sq mi), the five main islands are Hokkaido, Honshu, Shikoku, Kyushu, and Okinawa. Tokyo is Japan's capital and largest city, other major cities include Yokohama, Osaka, Nagoya, Sapporo, Fukuoka, Kobe, and Kyoto. Japan is the eleventh-most populous country in the world, as well as one of the most densely populated and urbanized. About three-fourths of the country's terrain is mountainous, concentrating its population of 125. 36 million on narrow coastal plains. Japan is divided into 47 administrative prefectures and eight traditional regions. The Greater Tokyo Area is the most populous metropolitan area in the world, with more than 37. 4 million residents. Japan has been inhabited since the Upper Paleolithic period (30, 000 BC), though the first written mention of the archipelago appears in a Chinese chronicle finished in the 2nd century AD. Between the 4th and 9th centuries, the kingdoms of Japan became unified under an emperor and the imperial court based in Heian-ky. Beginning in the 12th century, political power was held by a series of military dictators (shgun) and feudal lords (daimy), and enforced by a class of warrior nobility (samurai).