The Ministry of Education, Culture, Research, and Technology initiated the Indonesian Cultural House or RumahBudaya Indonesia (RBI) to strengthen Indonesian cultural diplomacy. This program aims to promote Indonesian cultural diversity, strengthen the existence of Indonesian culture, and increase the impression of Indonesian culture in 19 countries. This article explains the government's efforts to enhance Indonesian cultural diplomacy towards Japan through RBI and its impact on increasing the positive impression of Indonesian culture on Japanese society. The researchers used the concepts of cultural diplomacy and nation branding. This article applied a qualitative methodology with a case study approach and is supported by primary and secondary data validated by triangulation techniques. The results prove that although there are challenges in strengthening Indonesian cultural diplomacy, including the Covid-19, RBI in Japan has succeeded in increasing the Japanese public's impression of the noble Indonesian culture. RBI chose to conduct cultural exhibitions with the face-to-face program named "Day" and "Workshop" before the pandemic and the Online "Visit" and "Workshop" during the pandemic. This article shows that the success of RBI in strengthening the Indonesian cultural diplomacy in Japan is supported by the enthusiasm and positive appreciation of Japanese citizens for various Indonesian cultures.