This article traces the fraught history of the file system’s adoption by the Japanese Public Prosecutor’s Office (PPO) from the late 1940s to the early 1950s, when the U.S. General Headquarters (GHQ), the Supreme Commander for the Allied Powers, decentralized the PPO’s power and transformed it into a “democratic” judicial agency. This is also a postwar history of the introduction of Taylorism-derived scientific management to white collar office work and Weberian visions of bureaucratic rationality into government offices, as part of the democratization of public administration steered by various sections within GHQ. Among the key changes was a guarantee of the right to receive a “speedy trial.” The essay argues that, while that guarantee was meant to secure human-rights protections for the accused, the file system introduced to the PPO translated the constitutional imperative of the rights of the accused into the pursuit of efficient scientific management, in which democracy was an operationalized socio-technical achievement. This logistical channel led to the co-emergence of democracy and modern rational bureaucracy, with each evincing mutual cause and effect. American reforms invested technicality with the promise of “democracy,” but as this essay shows, senior Japanese officials envisioned it as a means to rebuild a centralized information network.