Innoshima Suigun Castle on Innoshima Island of Onomichi City, Hiroshima Prefecture, is a castle-shaped museum that displays documents about the Murakami Kaizoku, also known as the Murakami Suigun and Murakami Marine Force, who were active on the Seto Inland Sea during the mid-14th century.
At the top of a 150-step staircase stand three buildings: Honmaru, Ni-no-maru, and Sumiyagura. The Honmaru building is the Suigun Museum, and in it there are displays of materials related to the Murakami Marine Force, including armor, swords, tactical scrolls, and more. Next to Honmaru is Ni-no-maru, at which tactical councils have been recreated using samurai dolls, and at Sumiyagura visitors can look at photos of the Innoshima Suigun Festival. Additionally, at Konrenji Temple that lies at the foot of the castle, gorinto generational gravesites of the Murakami Marine Force have been enshrined.