Witnesses and victims in Japan and South Korea detail the suffering of an estimated 130,000 people held in forced labor colonies in North Korea and the anguish of relatives of people abducted by Pyongyang's agents.
The first commission of inquiry brought together by the United Nations to look into North Korea's record on human rights arrived in Tokyo this week after hearing harrowing testimony from survivors of the brutal penal camps operated by Pyongyang to suppress internal dissent and "wrong-thinking."
The experts week-long visit to South Korea coincided with the release of a new report by The Committee for Human Rights in North Korea titled "North Korea's Hidden Gulags: Interpreting Reports of Changes in the Prison Camps."
The report concludes that while two of Pyongyang's six known political labor colonies have been closed down, an "extremely high" number of prisoners remain incarcerated on political grounds, while countless others can only be listed as unaccounted for or have died in detention.
Isolation, punishment, execution
"Through this vast system of unlawful imprisonment, the North Korean regime isolates, banishes, punishes and executes those suspected of being disloyal to the regime," the report states. They are deemed 'wrong-thinkers,' 'wrong-doers,' or those who have acquired 'wrong-knowledge' or have engaged in 'wrong-associations,' the paper adds.
The report - compiled based on information provided by former inmates, defectors and a number of former camp guards and supported by information gathered by the interpretation of satellite imagery - says inmates "are relentlessly subjected to malnutrition, forced labor, and to other cruel and unusual punishment."
Thousands upon thousands more are forcibly held in other detention facilities. "North Korea denies access to the camps to outsiders, whether human rights investigators, scholars, or international media, and severely restricts the circulation of information across its borders," the committee stated.
Human rights activists say the report underlines the importance of the UN investigation, which in Japan is focusing on the abduction of dozens of Japanese nationals by North Korean agents since the 1960s. Pyongyang has reportedly used the abductees to train its own secret agents in how to fit into Japanese society and remain undetected as they went about their espionage tasks.
One of the people who will be testifying before the UN panel is Takashi Fujita, whose brother, Susumu, disappeared in February 1976 on his way to his part-time job as a security guard in Saitama Prefecture, north of Tokyo.
Missing for three decades
Despite increasingly frantic appeals to the police - although they had absolutely no inkling that he had been spirited away to North Korea - Fujita's family heard nothing about him for nearly three decades before two defectors emerged separately from the North with photos of a man they claimed was a Japanese national who had been taken to Pyongyang.
"Takashi Fujita met two intelligence officers of the Foreign Affairs Division of the Saitama Prefectural Police in December 2012, and was told that the National Research Institute of Police Science had examined the two photos by comparing them with Susumu's photos before he was abducted," Ken Kato, director of Tokyo-based Human Rights in Asia, told DW.
The institute concluded that both photos brought out of North Korea were in fact of Susumu Fujita, said Kato, who is assisting Takashi Fujita and other family members in their testimony to the UN panel.
The Japanese government, however, has only been able to officially designate 17 of its citizens as having been abducted by North Korea. Of those, five were released and returned to Japan in 2002, with North Korea claiming the rest had died of natural causes, of suicide or in accidents.
Activists such as Ken Kato believe there are more than 100 "highly probable" cases involving missing Japanese, while citizens of France, Italy, Holland, Lebanon, Thailand, Singapore, Macao and Malaysia are also believed to have been seized and taken to the reclusive state.
North Korea is also holding a US national, Kenneth Bae, who was detained in the town of Rason with a computer disk with images of hungry North Korean children. Tried on charges of planning a revolution to topple the regime, Bae was sentenced in April 2013 to 15 years' hard labor.
No access to North Korea
North Korea, for its part, has refused to allow members of the commission to access its prison camps, denied that it abuses the rights of its citizens and the state-run Korean Central News Agency has denounced the investigation as a "scheme" designed to derail the improvement that has been witnessed in recent weeks between Pyongyang and Seoul.
Kato has high hopes for the commission, which is headed by Michael Kirby, a former high court judge in Australia, and expects its conclusions to lay bare the sheer scale of the abuses that are being perpetrated by Kim Jong-un's regime - just as they were under the iron fist of his father, Kim Jong-il, and grandfather and founder of the nation Kim Il-sung.
And if those conclusions are as shocking as the activists believe them to be, then the rest of the world - including Pyongyang's few remaining allies - will no longer be able to turn a blind eye to the problem.
"I believe the commission's findings on North Korea's crimes against humanity will be a decisive blow to the regime," he said. "Even the Chinese do not want to be friends with such heinous criminals."