Any romantic aura that may have enveloped the gangsters in the past is falling away, the authorities say. They added that the Japanese increasingly see the yakuza simply as mobsters much like their counterparts in other countries, making money from drugs, gambling and extortion, particularly from their favorite target, Japan’s bloated construction industry.

“People are now seeing the reality that the yakuza are not chivalrous, but just an antisocial force,” said Kitakyushu’s mayor, Kenji Kitahashi, who said he was not intimidated by the death threat. He said the violence had turned many residents against the yakuza for hurting this former steel-making city’s efforts to lure new investment and jobs.

Japan has tried four times since the early 1990s to rein in the yakuza and has failed to make more than a dent in their numbers, currently about 80,000 (compared with estimates of 5,000 members of the American mafia at its height in the early 1960s). Like many Japanese gangs, the Kudokai even maintains its own public headquarters, the Kudokai Hall — a four-story, fortresslike white building surrounded by tall walls, barbed wire and security cameras — that sits in the center of Kitakyushu, a city of one million residents.

Until recently, the gangs were a quietly accepted fact of life. The yakuza were tolerated because they helped Japan keep its streets safe by imposing the same rigid rules and hierarchy on the criminal world that are seen in the rest of Japanese society. But as Japan has developed into a modern, middle-class nation, it has also refashioned itself into a society that relies on courts and lawyers to keep order, not medieval outlaws. The growing intolerance of the underworld has been evident in recent scandals in which a top television comedian and the national sport of sumo were forced to cut ties with gangsters.

Still, many admit, it has proven tough to completely cut ties.

“Society has used the yakuza for so long that it is hard to just get rid of them,” said Chikashi Nakamura, 75, head of a residents’ association in Kitakyushu that has campaigned to drive out the Kudokai.