Therefore, this article reviews Japan’s responses to the new space era, various perspectives on space and security, and the space democratic alliance, using the “preference-opportunity model” of rational choice theory as the analytical framework. This article sequentially analyzes Japan’s embedded autonomy and space development. By examining the phased development of Japanese satellites and the “Space Security Initiative” of Fumio Kishida’s administration, it clarifies the nation’s space autonomy. And from the perspective of procedural rationality and preferences, this article explores space cooperation under Japan’s pacifist constitution and the U.S.-Japan security arrangement, as well as Japan-led regional space international organizations, based on considerations of opportunity cost and information judgment. Finally, the article elucidates Japan’s international space cooperation under the considers of transaction coasts, focusing on the U.S.-led lunar program and the International Space Station.