In Japan, and pretty much ALL of Asia, the relationship between the security services and suspects is REALLY complicated.
One the one hand, it's the job of cops to catch the bad guys, but on the other hand, they also know that if they put the bad guys entirely "out of business", the cops will also be out of a job.
So what you end up with is this weird relationship where cops/security people will work to "contain" the bad guys, but they WILL NOT eliminate them outright... after all the bad guys are their "meal ticket"
A good example of this is in the series Tokyo Vice.
In a famous scene, the police officer Katagiri (played by the great Ken Watanabe) goes into a Yakuza lair after one of its associates stabs another Yakuza groups' men in a skirmish.
However, instead of arresting the whole group, Katagiri simply asks the Yakuza underboss "OK, who are you going to give us?"
I witnessed this first hand while transiting in China the other day.
Flying from Taipei to Japan, I changed planes in Shanghai. During the transit, I needed to undergo a secondary security scan of my hand-carried luggage.
During the scan, my backpack got flagged. The supervisor at the checkpoint handed my bag to another security officer who then proceeded to check its contents.
He pulled out my precision torax screwdrivers (which I need whenever I'm fixing my old 2011 Macbook Pro), and told me that unfortunately, these are not permitted in hand carried bags when transiting in China.
I replied that's fine, but I was a bit sad that they needed to confiscate one of the most expensive things in my bag (the torax driver set was like $50).
The security guy looked at me, signed and said quietly "那你必須要給我另外個東西。有什麼? [OK, but then you need to give me something else. What do you have?]"
I thought quickly for a second.
"可以給你這個軍人罐頭刀嗎 [What about this US Army P38 can opener?]" I asked. "有個刀片。。也很便宜! [it has a blade ... and only costs like $0.15]"
He took the can opener, then motioned for me to put the torax drivers away quickly.
He then shouted to his supervisor, who was still working the x-ray machine.
"找到了! [Item found!]" He then turned to me and gave me a quick smile. "你可以走了 [You can go now.]"