East Seto Sea

The eastern Seto Inland Sea lies between Honshu, Shikoku and Kyushu and opens toward Osaka Bay and the Kii Channel. Its waters form a sheltered passage linking the Pacific with Japan’s inner routes to the Sea of Japan. More than 3,000 islands, led by Awaji and Shōdoshima, break the 450-kilometre sea into channels and basins. The Setouchi region has a warm, dry climate with comparatively little rain.

From ancient times the sea connected Kansai, Chūgoku, Shikoku and eastern Kyushu. It also carried traffic between Japan, Korea and China, and foreign emissaries were recorded sailing through it. Waterborne power remained valuable during the feudal period: local suigun, or private navies, gained authority in many coastal districts, and the Kono and Kobayakawa families became especially prominent lords. In the Edo period the sea ranked among Japan’s busiest routes. Ships served Osaka, Sakai, Shimotsui, Ushimado and Tomonoura, while western daimyo travelled through it for their required journeys to Edo. Osaka’s offices for the domains and their rice revenues made the city an economic centre.

This traffic also followed the official route of Korean emissaries to the shogunate. Until the San’yō Main Line opened, the sheltered sea remained the principal connection between Kansai and Kyushu.