Research in language-in-education policy and planning (LEP) rarely examines how language teachers negotiate official policy statements on teaching methodologies. In this study, I investigate the current upper secondary school foreign language national curriculum in Japan that requires English classes to be conducted in English, implemented since 2013. I conduct in-depth, semi-structured interviews with three Japanese teachers of English (JTEs) to determine how they respond to the new initiative. I find that the JTEs struggle to make sense of the initiative's feasibility due to the vagueness of the policy directives, their perceptions of the disconnection between the recommended methodology and current national assessment mechanisms, and JTEs' own personal beliefs about first language use in the foreign language classroom. In order for teachers to feel empowered and supported in LEP delivery, it will be contingent on policymakers to provide consistent and coherent messaging, as well as sustained guidance at the meso (institutional) level to ensure policy realisation.