White paper on crime 2014 Part2/Chapter2
The Public Prosecutors Office consists of the Supreme Public Prosecutors Office (headed by the Prosecutor-General), eight High Public Prosecutors Offices (headed by a Superintending Prosecutor), 50 District Public Prosecutors Offices (headed by a Chief Prosecutor) with 203 branches, and 438 Local Public Prosecutors Offices. The different levels of public prosecutors offices correspond to the courts of comparable level.
In Japan, basically, public prosecutors hold the exclusive power to institute prosecution, i.e., indictment and summary prosecution. Public prosecutors decide not to prosecute where  the precondition for prosecution (e.g. victim's complaint for certain offenses) is not satisfied,  the act does not constitute an offense (or the suspect is not punishable due to insanity, etc.), or  the evidence is not sufficient to prove the offense. Public prosecutors may also decide not to prosecute even where there is sufficient evidence if they deem it unnecessary to prosecute based on factors such as the suspect's character, age, environment, gravity of the offense and circumstances after the offense (i.e., suspension of prosecution).