He works on compiling Japanese historical materials dating from the end of the Shogunate and the Meiji Restoration. As part of an academic agreement between the Historiographical Institute and the Korean Commission for the Compilation of National History, he previously conducted research on Japanese documents relating to the compilation of Korean history during the colonial era. This has enabled him to clarify the role of the Historiographical Institute and the colonial government. He is the author of Modern Japanese Historical Studies and the Compilation of Korean History by the Government-General of Korea (Japan and Korea during the Premodern Era, Tokyo: Yamakawa, 2007).