Guessing as to the plot direction of Six Four

By the mid-point in Hideo Yokoyama's Six Four we learn why the police (in unnamed Japanese city, 2002) are pushing, 14 years after theevent, to resolve the case of the kidnap and murder of a 7-year-old girl. The protagonist, a police officer and former detective now assigned to the lowly (ha!) area of media relations, Mikami, has been ordered to get the father of the kidnapped girl to agree to a visit from the highest-ranking police official. The father resists, at least at first, and Mikami finds that he's been shut out from all info on the case - which makes it almost impossible for him to work to get the father's trust and compliance. Through Mikami's many inquiries of present and former police officers, we learn that the police seriously screwed up the crime investigation, specifically, the device they'd set up to record any calls from the kidnapper failed and they missed the only chance to record his voice. Worse, they covered up this failure - and are concerned that now it will come to light, as HQ wants to close out this case. The failure of the device ruined the careers of at least 2 men. For many crime novels, this would be enough and we would now be moving toward a conclusion - but we have 300 dense pages to go! So what will happen? My guess is that the issue goes well beyond the failure of the recording device. Why would it fail? I'm guessing someone on the police force was involved in the kidnap plot and sabotaged the recorder - not suspecting that the plot would go awry and the girl would be murdered. HY holds my interest, but as noted in previous posts, and still very much true, it's almost impossible for an American reader to make sense of all the internal squabbles within this police department: It's never clear what office various people are working in, what the lines of authority are, where they various players stand in the PD hierarchy, what's the relation between this PD and Tokyo, and so forth. HY does not do much to differentiate the characters - he's strong on dialog but not on physical description, not does he make use of the crime-novel trope of giving the various characters quirks of behavior and interest or even notable "handles" or nicknames. Six Four remains an ambitious and for the most part engaging novel, but you have to read through a number of nearly opaque chapters.