This article examines the development of Japan’s early modern sugar industry from the late seventeenth to the mid-nineteenth century, arguing that it followed two distinct but interrelated paths: a colonial monoculture in the Amami Islands under Satsuma Domain control, and a decentralized household economy centred in eastern Shikoku. Drawing on domain administrative records, sugar-making manuals, household documents, and the journal of a samurai exile, the article traces how sugar-making knowledge entered Japan primarily through Ryukyuan intermediaries rather than directly from China, and how Japanese producers adapted, innovated, and hybridized imported technologies, including the three-cylinder mill, waterwheel-powered crushers, and claying and pressing methods for refining white sugar, to suit local conditions, labour regimes, and market demands. In Amami, the intensification of sugar production under Satsuma’s monopsony transformed the islands’ environment and social order, producing deforestation, food insecurity, debt bondage, and a dependent colonial relationship. On Shikoku and in mainland Japan, by contrast, farmers and agriculturalists developed a white sugar industry within the structures of village life. By situating these developments within broader global patterns of sugar technology diffusion, including possible Latin American and Jesuit connections, the article makes the case that Japan’s sugar industry, though modest in scale compared to the Atlantic or Chinese systems, was a site of significant technological innovation and merits fuller integration into global histories of sugar.