Seeing the museum as a public space for adult learning and education is not new, but always requires a contesting perspective when it comes to the continuing socio-political and historical oppression from colonial experiences. This paper explores the process of building a new history museum in South Korea that had suffered from Japanese colonial occupation from 1910 to 1945. The authors outline how the Center for Historical Truth and Justice (CHTJ), a vanguard civil organization dedicated to historical research on the Japanese colonial period and social action against colonialism, arrived at the 2018 opening of the Museum of Japanese Colonial History (MJCH) in Seoul. Generating and using a series of dialogues, suggested in institutional ethnography, the authors couple the topic of decolonization with the MJCH building process to interrogate the meaning of decolonization in contemporary South Korean society as well as learning for the identity formation of the new museum at the CHTJ. The paper discusses the museum educators' continuing performative role for public pedagogy to create the participatory museum.