When they first moved into Yoshikazu Kamimura's neighborhood of this big industrial city, the gangsters caused no trouble and an uneasy calm prevailed.

They decorated their house with a gang showing that they were affiliated with the Yamaguchi-Gumi, Japan's most feared criminal syndicate, but for a month there were no incidents.

Then the gangsters made a mistake: They refused to pay their bill to a neighborhood restaurateur and beat up the clerk who came to collect.

That set Kamimura to work. He organized parades, complete with baloons and placards, that went past the gangsters' house.Thousands of stickers were posted urging residents to report any violence to the police. Citizens massed by the hundreds and shouted pledges of cooperation. Finally, after their leader was arrested for threatening a jeweler who mustered nerve to complain, the gangsters moved out. Kamimura had won.

Such incidents are common in Japan, where the citizens play a growing role in combatting gangs. Encouraged by the police, they organize protest demonstrations and use many kinds of community pressure to uproot the gansters, or "yakuza," who settle in their neighborhoods.

Their strongest tactic is the public ostracism whose roots go deep in Japanese culture. The greatest fear of a Japanese, it is often said, is to be humiliated by one's peers and neighbors. In Japan, even hoodlums can't abide the disrespect of the people next door.

The anti-gang movements have been going on for years, ever since the greatgang wars of the 1960s. and recently the National Police Agency embraced the movements as an important part of police work. Police call it the "isolation policy."

Raisuke Miyawaki, director of the NPA's detective bureau, said the isolation policy often suceeds in destroying the influence of gangs without violence.

"We are seeking to create a society where gangsters cannot breathe," he said in a recent interview.

A new round of gang wars has given citizens cause for alarm this year. In Kyoto, the boss of the Yamaguchi-Gumi, Kazuo Taoka, was shot and wounded in a nightclub, and his followers and the police both began a manhunt for his assaillant , a member of a rival gang. The gangsters found him first; his decomposing body turned up on a mountain near Osaka last week.

Their internecine warfare is often gruesome. This week one mobsters body was found in a wooded area with the hands missing. Another gangster confessed killing the man in a gang feud and then throwing his severed hands into a vat of noodle soup which was later sold for 300 yen a bowl in a Tokyo street stall, police said. The killer said he wanted to destroy the man's fingerprints.

Roooting out gangsters has been hard because many citizens have secretly admired them as latter-day Robin Hoods who give help and jobs to lower-class outcasts and because many are employed by reputable businessmen to collect bad debts. Nevertheless, police say, in the last 15 years the number of gangs has been cut in half.

The gangsters themselves are curiosities in staid Japan. They dress in flashy suits and drive big American cars, an ostentation that sets them apart. They proudly post their gang symbols above doorways and many cover their bodies with extravagant tattoos. Their money comes from gambling, drugs, and prostitution.

The gangsters are society's dropouts and spurn legitimate careers. Police find that the risk of arrest and punishment has little effect on them and that cutting off their community links is often the only way of combatting them.

Over tha years, different tactics have been devised for cutting those links, Landlords refuse to renew the gangs' leases. Citizens boycott gangland bars. Neighbors harass gang members with telephone calls and signs demanding that the hoodlums move away. Companies stop hiring yazuka bouncers to keep peace at stockholders meetings - once a popular form of criminals' extortion.

The citizens try to hit where it hurts most. Japanese gangs historically have been deeply involved in theater and nightclub life, so in Kobe the city was induced to close public auditoriums to any show that had gang connections.

When one major gang tried to arrange a large Appalachian-style meeting, the local government and news media pressured them out. The gang arranged to hold the meeting in Seoul, South Korea, but police there also were induced to clamp down. Finally, the gang settled for a quiet little gathering in southern Japan.

Another gang planned an ostentatious pilgrimage to the famous Kinpiro temple on the island of Shikoku. The citizens responded by closing the bars and shops, leaving no place for the gangsters to celebrate after theirs religious celebration.

In Osaka last July, citizens and the news media descended on one gangster's house behind a parade of Boy Scouts, a band marching girls and large placards. The gangster was summoned into the street where a neighborhood proclamation was read to him. It said:

"We know your group caused gang fights and trouble for the citizens. It is a danger to the social order. So we have decided that you should dissolve at once and be good citizens or get out of our area."

The gangster did not move, but he reduced his criminal activities significantly, police said.

"The purpose is to make them uneasy," observed Hoshiro Ishikawa of the Osaka police department's crime prevention division. "It is to shame the gangsters, to give them a feeling that they cannot live there because it is too shameful."

In another area of Osaka, 10 landlords got together and agreed to rewrite rental contracts permitting them to cancel leases if tenants clearly demonstrated gangland characteristics, such as posting their symbols in public.

The police role in such movements is considerable. They advise citizen groups on tactics and promise to protect - with 24-hour guards, if necessary - anyone who feels that cooperation with authorities might invite gangsters' retaliation. Under a special Osaka law, one threatening word by a hoodlum is punishable by a jail term.

Tomoko Nakahata got into the fight against gangs when she discovered she had rented an office to members of the Tamb-Gumi, a small gang involved in gambling and prostitution in Sakai, an Osaka suburb.

She suddenly became the target of citizens who were angry that she had rented - unknowningly - to gangsters. So she organized neighborhood protest marches and told her unwanted tenants she would sue to break their lease on grounds that they had violated a clause requiring friendly relations with neighbors.

The case had a distinctly Japanese conclusion Detectives approached the Tamba-Gumi leaders and convinced them that they would lose the suit and be humilated. Rather than lose face, the Tamba-Gumi dissolved.