Criminal justice in Japan is strongly shaped by the way prosecutors organize their activities and perform their jobs. Their discretion is so great that analysts call the criminal proves one of "prosecutor justice." Prosecutors exercise this discretion within three overlapping ambits: their own organization, which is centralized and hierarchical and has a division of labor between operators, managers, and executives; a criminal court community that includes police, judges, and defense lawyers; and the broader contexts of economy, polity, and culture. For most of the postwar period there was considerable continuity in Japanese criminal justice, especially in the central roles played by prosecutors and police, the strong reliance on confessions, and a conviction rate that approached 100 percent. But significant changes started in the 1990s. Punishments became harsher, victims were more empowered, revelations of wrongful convictions and official misconduct started to stimulate increased transparency, and the advent of a lay judge system for trying serious cases provoked change in other parts of the process, from bail and discovery to interrogations and defense lawyering. Japan's lay judge system is in its infancy. Time will tell how much reform this fundamental change will arouse. What is clear is that Japanese prosecutors will continue to adapt to the shifting contexts of criminal justice. (Published Abstract)