Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the most populous metropolitan area in the world. It is the seat of the Emperor of Japan and the Japanese government. Tokyo is in the Kantō region on the southeastern side of the main island Honshu and includes the Izu Islands and Ogasawara Islands. Formerly known as Edo it has been the de facto seat of government since 1603 when Shogun Tokugawa Ieyasu made the city his headquarter but only became the capital and was renamed Tokyo after Emperor Meiji moved his seat to the city from the old capital of Kyoto in 1868. Tokyo Metropolis was formed in 1943 from the merger of the former Tokyo Prefecture and the city of Tokyo