In defence of the Japanese police: in each and every country, a fair deal of cops is nothing but a bunch of corrupted swines who are mostly after money or venting their issues on the weak more than justice and people's safety. EVERY country.
Take this ever so peaceful Belgium for example. Those tyrants arrested me for having pink hair. There was nothing else about my look or behavior, that made me different from everyone else at that party, and unlike me, many others did drugs which you could smell miles against the wind. For legally colored hair, they violently dragged me off the party ground (although I didn't resist at all), put me in handcuffs and tore my clothes off me in a cell, even insulted and threatened me. They also broke and entered without a warrant, to collect a tax that does not apply to me. I have also seen them threaten to beat up my 19-year-old friend for the cheeky remark "You should try (tightrope walking) too, it's fun" when they were harrassing tightrope walkers because their rope apparantly poses a greater threat than the loose Pitbull 10 yards further, which they didn't pay attention to at all while we were very much concerned. And did I mention seeing them hop in the brothels in Northern Brussels every now and then, alone and with a very happy face? For some reason those brothels have not been shut down despite the fact that illegal 16-year-old children were forced to work there... Hm. Strange.
Also, I am tattooed in a visible place and I tend to walk around like gangsta. Despite that, the Japanese police have never so much as looked at me. I can walk into a koban and ask for directions without worries of staying there longer than expected. At Narita airport, security went through my luggage in search for drugs, probably because of my tattoo and the hemp leaf necklace, but that's all.
So while I'm more than willing to believe any bad story about any police unit anywhere in the world, I also want to believe that that is not standard procedure as enforced by law.