General Didactics meets Subject Didactics: Lesson Study at the Intersection of Two Academic Fields

General and subject didactics in Japan have played various important roles in policymaking, academic research, and teacher training. Nevertheless, opportunities for collaboration between them have been limited. Meanwhile, lesson study – a series of activities for lesson development and reflection including planning, observing, and evaluating lessons – opened an arena where these two fields meet and intersect to bring new insights into lesson development and reflection. This article aims to clarify how lesson study could bridge both fields. The historical development of Jugyou Kenkyuu in Japan is first reconstructed in order to extract theoretical frameworks valid in the lesson study discourse. We then present lesson study practice at School X where researchers from general and subject didactics collaboratively joined the lesson study, examined their own role arrangements, and found distinctive self-dispositioning. The case revealed several major modes of collaboration including complementary relationships, different communication styles, and integration. The article ends with a reflection on further perspectives for future work in lesson study.