The Seto Inland Sea has long served as a vital corridor of maritime commerce, despite its many navigational hazards. In the past, seafarers ensured smooth passage through these waters by relying on guidance from three groups of pirates, who possessed the skills and local knowledge to use the currents to their advantage. The term “pirates” refers to three major maritime clans: the Shiwaku Navy, who controlled the waters around the Shiwaku Islands off the coast of present-day Kagawa Prefecture; the Murakami Pirates, who dominated the Geiyo Islands around what is now the Shimanami Kaido; and the Kono Navy, who held sway in the seas near Matsuyama in Ehime Prefecture. Our guide to these waters will be Junko Yamada, an expert on the pirates of the Inland Sea. We will explore how the Murakami Pirates shaped Japanese history, visiting the remains of their island castles and other related sites.