STEP ONE: The public prosecutor's office investigates suspects, deciding whether or not to indict them on charges.
STEP TWO: The public prosecutor's office, after careful consideration of the evidence, decides it cannot secure a conviction of the suspects in question.
STEP THREE: A private individual or a group, ticked off at the decision of the prosecutors, files a motion with the Committee for the Inquest of the Prosecution to reexamine the prosecutor's decision.
STEP FOUR: The Committee for the Inquest of the Prosecution, whose sole reason for existence is to question the decisions of prosecutors to not prosecute, comes to the conclusion that the public prosecutor's office should reconsider its decision. (This is what happened yesterday as regards the three former executive of Tokyo Electric Power Company, owner and operator of the Fukushima Daiichi nuclear power station - Link)
STEP FIVE - The public prosecutor's office, upon being told that its decision to not prosecute was wrong, replies, "No, we got it right the first time: there is no basis for a prosecution" and rejects the Committee for the Inquest of the Prosecution's conclusion.
STEP SIX - The Committee for the Inquest of the Prosecution, pissed off that the public prosecutors refused to take its conclusion seriously, says, "Oh yeah? Why did we even bother to ask you to reconsider anyway? We'll just appoint our own, private sector lawyers to indict and prosecute the defendants. So there!"
STEP SEVEN - The Committee for the Inquest of the Prosecution trudges over to the local bar association office to find three lawyers to serve as prosecutors. The local bar association tells the Committee to not expect much, as no competent lawyer with a thriving practice has the time to be a prosecutor. Furthermore, no lawyer concerned about his/her professional reputation would agree to step in after the public prosecutors have already twice determined there is no case. The Committee asks the bar association to try anyway.
STEP EIGHT - Three lawyers who are either incompetent, do not care about their reputations or have been browbeaten into accepting the role by colleagues saying, "Look, just accept the assignment, OK? Just go through the motions, fail and the Committee is off all our backs. We'll make it up to you later" agree to look at the evidence.
STEP NINE - Since the three lawyers were hired to file charges, they unsurprisingly find the evidence to prosecute compelling and indict the suspects.
STEP TEN - Either from a personal lack of smarts, zero cooperation from a resentful public prosecutor's office or the total absence of giving a damn, the three lawyers fail to convince a judge of the merits of the charges and the suspects are all found "Not Guilty."
And no, the above is not just a cynic's barking. This what happens when an interesting question -- "Is there not some way that average citizens, certain that the decisions of public prosecutors to not prosecute are the result of political interference or other nefarious forces, can demand that the prosecutors either do their jobs or stand aside?" is not followed up by the question "OK, what could go wrong?"