The group that represents Koreans loyal to Pyongyang is accused of abetting the Kim regime by providing funds and banned technology. It is also linked to the abduction of Japanese, organized crime and drug distribution.
As an ethnic North Korean, Kim Myong-chol says he lives in "a hostile environment" in Japan. There have so far been no reports of Japanese targeting North Koreans living here, but as concern over the possibility of a missile or nuclear attack rises, Kim says incidents have happened in the past and are possible to occur again.
"There have been attacks by right-wingers on children from North Korean schools at times of tension in the past, but it has been quiet so far," he told DW. He added that police have had a higher presence close to schools affiliated with Chongryon, the association that represents North Korean residents of Japan, since previous incidents.
When Pyongyang confirmed in September 2002 that its agents had abducted 13 Japanese citizens, there was an upsurge in anger aimed at the North Korean community in Japan. There were demonstrations outside the fortress-like headquarters of Chongryon, which serves as North Korea's embassy in Japan as the two nations have no diplomatic ties, while schools received threatening phone calls and pupils were roughed up on their way to and from schools.
US sets on diplomacy in N.Korea dispute
Kim, who is executive director of The Centre for North Korea-US Peace and an unofficial mouthpiece of the Pyongyang regime, said he has been a target of the Japanese authorities in the past and that police once searched his home for communications equipment on the suspicion that he was an agent.
Despite the pressure that he lives under, Kim is adamant that North Korea will emerge triumphant in this latest confrontation with the United States, South Korea, Japan and a growing number of other states arrayed against it.
"We are confident that the North Korean government will defeat the US; we have no doubts about it at all," he said.
There are an estimated 610,000 Korean residents in Japan; the majority of them are descendants of forced laborers brought here during Japan's colonial occupation of the Korean Peninsula. Around 150,000 still swear allegiance to the North Korean regime.
And many in Japan are concerned that North Korean doctrine and adulation for the ruling family of Kim Jong Un are being instilled in the younger generation of North Korean children in Chongryon's schools.
Across Japan, there are about 60 schools - ranging from kindergartens to universities - that are affiliated with Chongryon. Portraits of Kim Il Sung and Kim Jong Il, the present dictator's grandfather and father respectively, look down on pupils in every classroom and students are taught an alternative view of the world. In history classes, for example, they learn that South Korea and the US started the Korean War in 1950 by invading the North.
Around 10,000 children of ethnic Koreans attend the schools, down significantly from the 40,000 that attended Chongryon schools in their heyday, in the 1970s.
If Ken Kato had his way, the institutions would be abolished. "It is like having a school for the so-called Islamic State or al Qaeda in Japan," he told DW. "The children at these schools are taught to hate Japan, to hate the US and to carry out a revolution to invade South Korea so that they can 'liberate' its people.
"They teach these children to use violence and promote values that are the opposite of peace, freedom and democracy," said Kato, who is director of Tokyo-based Human Rights in Asia and a member of International Coalition to Stop Crimes Against Humanity in North Korea.
There are also suggestions that teachers at North Korean schools in Japan are assisting the regime to carry out criminal activities, Kato noted.
So Kay Se, the former headmaster of Shimonoseki Korean School, is wanted by the police here for allegedly helping to smuggle 250 kilograms of amphetamines into Japan, while Kim Kil Uk, the former head of Osaka Korean School, is on Interpol's wanted list in connection with the abduction of Tadaaki Hara from Miyazaki Prefecture in June 1980.
Hara is just one of the dozens of Japanese that North Korea abducted to instruct its agents to infiltrate society here. Pyongyang claims he died in 1986 but has provided no evidence.
Both So and Kim are believed to have escaped to North Korea.
Kato is among those who believe that more should be done to stop North Korean residents of Japan abetting the regime in Pyongyang.
Billions sent to Pyongyang
Billions of yen earned by North Koreans living in Japan - through means both legitimate and illegitimate - have been funneled to Pyongyang, although the Japanese government last year closed one loophole by banning bank remittances to North Korea. According to Kato, as many as 40 percent of the members of organized crime groups in Japan are Korean, earning money from loan-sharking, illegal gambling operations, prostitution, protection rackets and drugs.
Narcotics, in particular, have proved a significant source of income for Pyongyang.
In December 2001, a North Korean vessel disguised as a fishing boat opened fire on Japanese Coast Guard vessels about 300 kilometers off southern Japan. In the ensuing six-hour firefight, the 15-strong North Korean crew was killed and the boat was sunk.
When it was subsequently raised, it was discovered that the vessel had been fitted with a concealed anti-aircraft gun and stern doors to allow a smaller boat to be deployed, presumably to deliver drugs or agents onto a Japanese beach.
In April 2003, a North Korean freighter was boarded off Australia and authorities found 50 kilograms of heroin, with a street value of tens of millions of dollars.
In both cases, the North Korean government denied any involvement. In other cases, North Korean diplomats have been accused of using the diplomatic bag to import drugs that are then sold.
Through front companies, Chongryon is also suspected of illegally procuring technology that could benefit the North's nuclear and missile programs.
Kim Myong Chol, a Korean writer and editor based in Japan, angrily denies all the accusations, answering "not true" when asked about the purchase of banned technology, the transfer of funds to North Korea, Chongryon's involvement in the abduction of Japanese nationals or the suggestion that North Korean children are being trained to embrace the violent overthrow of Pyongyang's enemies.
"I overheard some young children the other day discussing where they planned to hide when a missile struck," he said. "It is a tragedy that they even have to think these things."
But there is a bitter irony in North Korean residents' unquestioning support for the regime in Pyongyang, he pointed out.
"For years, they have been smuggling technology to the North and sending money back to fund the development of its nuclear weapons and ballistic missile programs, but the missiles they have paid to build will not make any distinctions if they fall on a Japanese city," he said. "They will kill North Koreans just as easily as the rest of us."