In the 1980s, Japan's social welfare system was adapted to international standards, and fundamental social institutions, such as the national pension fund, were made accessible to foreign nationals. However, various circumstances have resulted in approximately 30,000 foreigners still being denied access to the national pension fund today. Most of those affected are first-generation Zainichi Koreans. This work highlights the circumstances that have led to this social exclusion by examining the case of five Korean women from Kyoto who fought in court for inclusion in the national pension fund. Zainichi Koreans experienced both social integration and exclusion depending on the prevailing zeitgeist. This court case demonstrates that the Japanese judiciary is unwilling to take full responsibility for the social security of Zainichi Koreans. An analysis of post-war Japanese social policy reveals that international pressure and local engagement have particularly contributed to improvements in the legal and social status of Zainichi Koreans.