Tokyo is one of 47 prefectures in Japan and has been the capital of Japan since 1869. Until 2018, Greater Tokyo was ranked first in the world’s most populous metropolitan area. Tokyo was the seat of the Japanese Emperor, Japanese government, and Japanese Parliament. Tokyo includes parts of the Kanto region, the Izu Islands and the Ogasawara Islands. Tokyo was previously called Edo when Shōgun Tokugawa Ieyasu made the city his headquarters in 1603. The city changed its name to Tokyo after Emperor Meiji made it his capital and moved his throne from Kyoto in 1868. Tokyo Metropolis was formed in 1943 from the merger of the cities the. . former Tokyo Prefecture and Tokyo City. Tokyo is often referred to as a city, although it is officially a “metropolitan prefecture” which is very different from a regular city and combines elements of both city and prefecture.