Tokyo Metropolis (東京都 Tōkyō-to) is one of the 47 prefectures of Japan,[5] and is both the capital and most populous city of Japan. The Greater Tokyo Area is the most populous metropolitan area in the world.Formerly known as Edo. Tokyo Metropolis was formed in 1943 from the merger of the former Tokyo Prefecture(東京府 Tōkyō-fu) and the city of Tokyo (東京市 Tōkyō-shi).