I was at Yokota AB in 1983. A friend lost his wallet one night while ‘out on the town.’ He went back the next day to the bar. Someone was sitting on the bench outside, guarding his wallet. He tried to give a reward, but it was refused.
Of course, the same guy was out another night, and looked down an alley where three men were beating on another. The three came after my friend, and beat him, as well. The police told him that it was yakuza, likely collecting money.
The Yakuza has been around a long time and will stay around for a long time to come. Interesting bunch they are. I use to think that they were more overblown than actually relevant, similar to the La Cosa Nostra. Now I know better. They are around, there are a lot of them, and they are more widely spread than most people can imagine.
There was a half burned up Pachinko parlor near use when we moved there in the 90's. It was odd because the Japanese normally tear down and rebuild very quickly. This place just sat there. A guy I knew who was married to a local told me the reason no one would touch it is because it was the result of some turf dispute among local rivals in the underworld (Yakuza). No one would touch the place.
The Yakuza has ties to the Norks. I'm sure they make a lot of money with the illegal trade that goes on keeping Fat Boy Kim fat and happy and drugs and guns coming in Japan.