Saikaido is one of the main 'circuits' of Tokugawa Japan. Literally translated, it means 'western sea road', now known as Kyushu. Similarly, Hokkaido is the northern sea circuit. Nankaido, which includes all of Shikoku, is the southern; Tokaido is the eastern, made famous by the wood-block prints of Hokusai and Hiroshige.
