A small group of protesters, clutching hand-written posters and a tinny microphone, gathered outside the bleak, gray building that houses the North Korean embassy in central Berlin on Wednesday afternoon. Cars and trucks thundered past, almost drowning out their shouts and chants for "reunification" and "free North Korea."

As the mostly elderly men and women determinedly soldiered on outside, in the lobby of the cheap backpacker's hostel next door, Myeong Chul Ahn briefly scrolled down his Facebook page, as a group of young tourists wandered past. The 46-year old, elegant in a dark suit, sporting a chunky silver watch, grimaced briefly, then looked up: He still carried the trauma, he said, and the guilt. "Many nights, I dream that I am facing a firing squad."

Myeong Chul Ahn spent eight years working as a guard in several prison camps, often referred to as Gulag, in North Korea, one of the world's most repressive regimes. Anyone who tried to flee the brutal labor camps would be executed immediately by a firing squad.

Abuse, near-starvation, torture

According to Human Rights Watch, South Korean officials estimate that between 80,000 and 120,000 people are imprisoned in the labor camps. The camps, operated by the country's National Security Agency, are characterized by systematic abuse, including near-starvation, sexual abuse, torture and executions.

His face impassive, Myeong Chul Ahn recalled the camp, which for years, he, the son of a high-ranking party member who had lead the privileged life of the "top 1 percent", was proud to call his work place: Political prisoners, would-be defectors and their entire families - "grandparents, aunts, many children were born in the camp" - were locked away for life, he told DW, and forced to do hard, grueling labor.

At first, he said, he had little sympathy for those he had been indoctrinated to consider "criminals". Without pity, he watched them starve and work themselves to death - on an average day, he says, as many as five people died. Sometimes, he would beat them up, "for fun."

But gradually, over the years, he told DW, he began talking to the captives to relieve the boredom and monotony of his work. "90 percent of them didn't even know why they were there", he said. "That made me question certain things."

Brutal response to criticism

But the turning point came in 1994 when his father, who he says was in charge of the country's food distribution system, dared to criticize the regime: It was the early 1990s and the country was facing a famine. But in a totalitarian system that allowed no dissent whatsoever, the consequences were swift and brutal: Myeong Chul Ahn's brother and mother were arrested, his father committed suicide before the regime got to him. He knows he will never see his brother and mother again, he shrugs, impassively, "you can never leave such a camp."

And so Myeong Chul Ahn fled the country. He was lucky, he says, he knew one of the border guards on duty, who waved him through to China and on to South Korea, where he soon joined other defectors fighting against the regime.

Another such defector turned activist is Il Lim, who, together with Myeong Chul Ahn, is touring round Germany this week, meeting parliamentarians and officials in the German foreign ministry. It would be good, the 47 year old told DW, for Germany to support reunification of North and South Korea. Myeong Chul Ahn agrees: "And then the Gulags could be turned into memorials, like Auschwitz, to serve as a testimony, so people never, never forget."

But while they share a common objective - an end of the North Korean regime - their stories couldn't be more different: While Myeong Chul Ahn enjoyed a lavish, privileged life, which included such luxuries as dolphin meat and a housekeeper, Il Lim was barely surviving in Pyongyang amid the regime's man-made famine of the 1990s, when hundreds of thousands, possibly more, starved to death.

“We were always hungry”

Although he had a relatively good job working as a carpenter, he and his wife and two-year old daughter "were always hungry."

And so, when the offer came in 1996, he was quick to agree to a job working on a construction site in Kuwait. It wasn't out of patriotism, although he, like everyone else, had learned to unquestioningly love the regime's leader Kim Jong-il as his father. But rather, because he thought he might finally be able to feed his family.

But the promise of good money turned out to be nothing but propaganda: Instead, he and thousands of others were crammed into a labor camp surrounded by barbed wire, run and guarded by the North Korean government in Kuwait.

Similar North Korean "slave labor" still exists today, according to Martin Lessenith from the German chapter of the International Federation for Human Rights (IGFM), which organized the two dissidents' trip to Germany. Leasing out North Korean forced labor to Russia and the Gulf, he added, was a major source of income for the regime.

Il Lim says conditions were dire: For five months, he told DW, he worked long hours, without ever receiving any wages. And so, one day, he bribed one of the guards and made his way to the South Korean embassy in Kuwait.

"You can't imagine the beauty of freedom"

It was, he says, a very difficult decision: He knew he would most likely never see his family again, but he craved freedom. "You can't describe the taste of freedom, the freedom to say what you want, to do what you want. If you've always been free," he said, smiling slightly, "you simply can't imagine the beauty of freedom."

He spent several years working odd jobs in restaurants and construction sites in Seoul, until he started working as a writer. He proudly showed his latest book, a novel called "Reunification."

But the price for his freedom meant he lost his wife and daughter completely: His wife was most likely forced to divorce him, but he doesn't know for sure, as he is unable to contact them. "I think about my daughter a lot, I keep her in my heart."

Later, long after the determined band of protesters had rolled up their banners and left, the two men posed for a picture outside the North Korean embassy. Standing beside the imposing gate, the two men frowned, side by side, giving their thumbs down.

If things had worked out differently, Myeong Chul Ahn says he might have ended up working in the bleak, gray building behind the gate, "maybe as a military attaché, even ambassador one day", defending the regime's abuses of ordinary citizens like Il Lim.

DW repeatedly reached out to the North Korean embassy in Berlin for a comment, but until now hasn't received a response.