No. The Yakuza generally do not participate in civilian affairs, nor are they interested in "policing", except where someone becomes a personal nuisance to a higher-up or someone disrupts their business.

Their primary interest lies in the financial side of mizu-shobai type establishments, gambling, and money laundering.

They also offer thug-work-for-hire, which is helpful when the police aren't, but you've got to be careful dealing with them because there tend to be hidden costs to their "help".

* whoops. replied at the wrong level :P