Because of these reasons, the maritime peoples of the islands prospered from marine transportation and commerce, and also acted as navigators of passing ships with tolls, supplementing their income with occasional piracy.

In his counter-attack against the Hosokawa, Murakami Masafusa (1413-1515) provided naval support and reconstructed Noshima Castle as a base of operations.

The main residence of the Noshima Murakami was on the neighboring island of Hakatajima, and shipyards and warehouses were constructed on Ujima.

In the Sengoku period, the Noshima Murakami provided invaluable support to the Mōri clan at the 1555 Battle of Miyajima.

Toyotomi Hideyoshi was dispatched to conquer the Mōri, and initially attempted to bring the Murakami to his side.