Katsumoto Port is a natural harbor located at the northern tip of Iki Island. At the mouth of the bay, there are three islands: the uninhabited island of Tatsunoshima, which is popular for cruises; Wakamiyajima, which has a guard post for the Japan Ground Self-Defense Force; and the uninhabited island of Nagarasujima. There is a history of whaling here, and fishing has been carried out here since the Yayoi and Kofun periods. Currently, it is one of the leading production areas in Japan for yellowtail, grouper, sea bream, swordfish, and bluefin tuna (line-caught). ・750 years ago, during the Mongol Invasion of Japan, Mongol troops landed at Seibo-gu Shrine in the Katsumoto area. ・During the Edo period, it was a port of call for Korean envoys, who called at the port 11 times on their outbound journey and 8 times on their return journey over a period of about 200 years. In 1894, the Fukagawa Kisen and then the Tsushima Shosen (now Kyushu Mail Order Company) began service on the Hakata⇔Iki/Tsushima route, but as the ships used became larger it became impossible to make port calls, and the service was discontinued in 1975.