“Japan …has limited wire-tapping. There is no plea-bargaining allowed. There is no witness protection or witness relocation program. There is no incentive for a low-ranking yakuza to rat out the people above him and a hundred reasons for him to keep his mouth shut. For these reasons, most investigations often peter out before really getting off the ground….
It’s not a crime to be a member of a yakuza, although being a proven member has disadvantages in normal daily life.”
From the same interview as the last post on the yakuza. I must say that I’d heard much dodgier theories than that, including that some of the money from pachinko goes straight into police pockets