JapanJap. Nihon or Nippon, country, 145,833 sq mi (377,835 sq km), occupying an archipelago off the coast of E Asia. The capital is Tokyo, which, along with neighboring Yokohama, forms the world's most populous metropolitan region. Historically, the divine design of the empire—supposedly founded in 660 B.C. by the emperor Jimmu, a lineal descendant of the sun goddess and ancestor of the present emperor—was held as official dogma until 1945.