Chapter 1 observes that the Japanese archipelago has been represented unduly as an “islanded” entity, due to the prevalence of exceptionalist concepts such as national seclusion or sakoku. It presents Japan as a terraqueous economy by outlining the history of marine nutrients from fishing grounds along the Kuroshio and Oyashio currents, which remained prominent factors in the expansion of agrarian production until the twentieth century. It suggests different possibilities to embed the archipelago’s early modern and modern histories conceptually in its hydrological environments: Teleconnections such as the East Asian Monsoon offer historiographical challenges to Eurocentric models like the “East Asian Mediterranean.” Likewise, maritime currents are agents in the making and remaking of Japan’s terraqueous economy. Their seasonal rhythms create specific environments of risk in which the archipelago’s marine resource and shipping industries developed their business practices. The Kuroshio offers special possibilities, because it represents both a modern scientific concept and an early modern source term – its study can therefore build on intellectual and vernacular virtual geographies.