Based on Japanese and Portuguese sources, this paper aims at recovering local categories of bondage in order to identify mechanisms by which people were subjected to bonded labour in early modern Japan. The analysis focuses on crossing local forms of bondage, here referred to as genin, and the processes of subjecting individuals to this condition, the so-called called geninka, with the European notion of slavery and enslavement. Local forms of subjection to bondage are drawn from the analysis of early seventeenth-century Tokugawa legislation dedicated to the suppression of human trafficking networks. These documents use a number of labels such as genin, hōkōnin, wakatō, chūgen, hikan, and komono, all references to people subjected to various forms of bondage. At the same time, a crucial debate among members of the Society of Jesus in India offers the opportunity to scrutinise the application of the historical and legal European concept of slavery and enslavement to Japan, a region beyond the secular authority of colonial empires. Ultimately, slavery reveals itself as one of the many categories used by early modern actors to interpret and regulate labour arrangements in the budding Christian communities created by missionaries in the Iberian world.