In Japan, the authority to execute police duties is geographically divided into 47 prefectural jurisdictions, each of which is supervised by a prefectural public safety commission. The law also empowers the national government to establish a central police organization to control and supervise prefectual police organizations. The National Police Agency, supervised by the National Public Safety Commission, performs this function. Police responsibilities range from crime prevention to the protection of citizens and counter-intelligence regarding terrorism and espionage. The police are empowered to investigate all illegal acts punishable under Japan's judicial system. In order to ensure political neutrality in the performance of duties, police agencies are under the supervision of public administrative commissions that formulate basic policy and regulations for police operations. A section of this paper addresses the effective management of the police investigation. It considers collaboration with prosecutors, citizen confidence in police proficiency and competence, and police training. In discussing cooperation between the police and the prosecutors in Japan, the author notes that the police and the prosecutors cooperate closely and well in Japan. Police begin consulting with prosecutors as appropriate in the early stages of an investigation. Prosecutors can make general suggestions to the police in the course of an investigation by clarifying the legal standards that must be followed if a case is to produce an effective prosecution. In discussing the effective screening of cases in collaboration with prosecutors, the paper briefly addresses the effective clearance of crimes that follows due process of law, the diversion of minor offenses through a simplified process, and collaboration with prosecutors in non-indictment dispositions.