This article highlights the cross-disciplinary methodological potential of Third World approaches to international law (TWAIL) and microhistory by studying the active and complex exercise of agency by victims in an understudied historical instance of post-war justice, namely, the Singapore ‘Sook Ching’ trial or Nishimura trial. This trial dealt with the arbitrary massacre of Chinese residents by the Japanese military during the Second World War. Using TWAIL and microhistory methods, this article analyses trial transcripts and archival material on the Nishimura trial, with a focus on the trial experiences of witnesses, survivors, and community representatives. By studying the Nishimura trial as mobilization and meaning-making opportunity, this microhistory draws attention to the exercise of social and political agency by the Chinese community under difficult post-war conditions and British colonial rule. Chinese community leaders represented the community as collectively victimized and united in the pursuit of post-war justice. However, a close analysis of trial transcripts reveals tensions within the community and the need for a more complex understanding of victimhood.