The introduction points out that changing human presence in the Pacific affected Japanese politics throughout the nineteenth century. In particular, the whaling boom of the 1820s to 1840s caused security anxieties among policymakers, while Japanese whalers by mid-century struggled with declining catch rates. Building on scholarship from Oceania, the introduction suggests thinking of Japan not as an island, but as a “Sea of Islands,” a terraqueous zone awash in currents such as the Kuroshio south of Honshu that allocate warmth, humidity, and nutrients and create a specific, though fluid, offshore geography in which consequential historical conflicts and competitions unfold. It lays out a set of questions that emerge from such framing and suggests conceptualizing the history of the Kuroshio’s catchment area as an oceanic frontier. This brings the historical significance of ocean, islands, and human travelers beyond the traditional human habitat to the fore. Since the seventeenth century, ongoing attempts at controlling this frontier has informed business practices and expansionist ideologies of Japan.

Chapter 8 observes the emergence of frontier tycoons toward the close of the nineteenth century, carried by a wave of “South Sea Romanticism” in literature and politics, propagated publicly by a pathos of drift and discovery. Fueled by insurgent demands of popular rights in the 1870s, grassroots expansionists claimed a “national right” to adventure and opportunity in the ocean frontier. Petty entrepreneurs of questionable reputation and ambivalent attitudes towards the law “opened” remote isles where state control faded. Others, like the entrepreneur Koga Tatsushirō who appropriated the Senkaku (Diaoyu) islands in 1895, enjoyed governmental backing. Such island colonies were eventually absorbed by the empire’s corporate infrastructure and were refashioned as sandboxes for colonial administration. “Rogue entrepreneurs” meanwhile traveled as far as the Caroline Islands in Micronesia, where one businessman, operating below the government’s radar, eventually facilitated the installation of a Japanese South Seas Protectorate. The chapter argues that the Japanese empire’s modalities of expansion carried the imprint of these experiences.