This thesis offers insights into the institutional and policy changes associated with anti- trafficking and anti-slavery paradigms by drawing attention to discursive institutionalism. These insights derive from the constructed dominant discourses on human trafficking and modern slavery in Japan from 1990 to 2017. Two strands of discourse have become dominant there as a consequence of political activism since the early 1990s: Filipina entertainers as ‘sex trafficked victims’ and interns and trainees in the Technical Intern Training Programme (TITP) as ‘modern slaves’. Taking a critical view of these discourses, this thesis answers the questions of how and why institutional arrangements associated with trafficking and modern slavery have changed in Japan. It argues that, in the context of a discursive shift regarding how to treat these workers, institutions and policies gradually changed to provide remedies to foreign interns and trainees under the purview of TITP by 2017, whilst entertainers largely remained subjects of criminalisation and deportation. By looking at the empirical transformation by 2017, this thesis argues that the discourse about trafficking and modern slavery was significant in making known the needs to protect unskilled migrants. While not officially admitting that labour trafficking and modern slavery exist in Japan (due to its zero-immigration principle), the government in 2017 revealed its intention to establish an action plan to fight trafficking and modern slavery, following the initiatives of United Nations’ Sustainable Development Goal (SDG) 8.7. Through the lens of human trafficking and modern slavery and the related changes in policies and institutional arrangements since the early 1990s, this thesis examines the role of the state in solving problems related to unskilled migrants. In this sense, the study empirically illuminates the trajectory of the government’s current shift towards officially accepting unskilled labourers in response to Japan’s dwindling workforce.