He ran the first chance he got.

The summer sun beat down on the shallow, sea-fed fields where Kim Seong-baek was forced to work without pay, day after 18-hour day mining the big salt crystals that blossomed in the mud around him. Half-blind and in rags, Kim grabbed another slave, and the two men — both disabled — headed for the coast.

Far from Seoul, the glittering steel-and-glass capital of one of Asia's richest countries, they were now hunted men on this tiny, remote island where the enslavement of disabled salt farm workers is an open secret.

"It was a living hell," Kim said. "I thought my life was over."

Lost, they wandered past asphalt-black salt fields sparkling with a patina of thin white crust. They could feel the islanders they passed watching them. Everyone knew who belonged and who didn't.

Near a grocery, the store owner's son came out and asked what they were doing. Kim broke down, begged for help, said he'd been held against his will. The man offered to take them to the police to file a report. Instead, he called their boss, who beat Kim with a rake — and it was back to the salt fields.

"I couldn't fight back," Kim said, in a recent series of interviews with The Associated Press whose details are corroborated by court records and by lawyers, police and government officials. "The islanders are too organized, too connected."

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Slavery thrives on this chain of rural islands off South Korea's rugged southwest coast, nurtured by a long history of exploitation and the demands of trying to squeeze a living from the sea.

Five times during the last decade, revelations of slavery involving the disabled have emerged, each time generating national shame and outrage. Kim's case prompted a nationwide government probe over the course of several months last year. Officials searched more than 38,000 salt, fish and agricultural farms and disabled facilities and found more than 100 workers who had received no — or only scant — pay, and more than 100 who had been reported missing by their families.

Yet little has changed on the islands, according to a months-long investigation by the AP based on court and police documents and dozens of interviews with freed slaves, salt farmers, villagers and officials.

Although 50 island farm owners and regional job brokers were indicted, no local police or officials have faced punishment — and national police say none will, despite multiple interviews showing some knew about the slaves and even stopped escape attempts.

Slavery has been so pervasive that regional judges have shown leniency toward several perpetrators. In suspending the prison sentences of two farmers, a court said that "such criminal activities were tolerated as common practice by a large number of salt farms nearby."

The AP findings shine a spotlight on the underbelly of an Asian success story. After decades of war, poverty and dictatorship, South Koreans now enjoy a vibrant democracy and media, and an entertainment industry that's the envy of the region. But amid the country's growing wealth and power, the disabled often don't fit in.

Soon after the national government's investigation, activists and police found another 63 unpaid or underpaid workers on the islands, three-quarters of whom were mentally disabled.

Yet some refused to leave the salt farms because they had nowhere else to go. Several freed disabled slaves told the AP they will return because they believe that even the salt farms are better than life on the streets or in crowded shelters. In some cases, relatives refused to take the disabled back or sent salt farmers letters confirming that they didn't need to pay the workers.

Kim's former boss, Hong Jeong-gi, didn't respond to multiple requests for comment through his lawyer, but argued in court that he didn't confine the two men. Hong is set to appear next week in court to appeal a 3½-year prison sentence.

Other villagers, including paid salt workers, say farmers do the best they can despite little help from the government, and add that only a few bad owners abuse workers. Farmers describe themselves as providing oases for the disabled and homeless.

"These are people who are neglected and mistreated, people who have nowhere to go," Hong Chi-guk, a 64-year-old salt farmer in Sinui, told the AP. "What alternative does our society have for them?"

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On the night of July 4, 2012, a stranger approached Kim in a Seoul train station where he was trying to sleep; Kim had been homeless since fleeing creditors a decade earlier. The man offered him lodging for the night and promised him food, cigarettes and a "good job" in the morning.

Hours later, Kim stood in the muck of a salt farm owned by Hong, who had paid an illegal job agent the equivalent of about $700 for his new worker, according to court records.

Kim, visually disabled and described in court documents as having the social awareness of a 12-year-old, had no money, no cellphone and only the vaguest idea of where he was.

The afternoon of his first full day on the farm, Hong erupted as Kim struggled with the backbreaking work, according to the prosecutors' indictment that a judge based Hong's sentence on. The owner grabbed him from behind and flipped him onto the ground, screaming, "You moron. If I knew you'd be so bad at this, I wouldn't have brought you here."

In the next weeks, Hong punched him in the face for not cleaning floors properly. He beat him on the buttocks with a wooden plank for raking the salt in the wrong way.

"Each time I tried to ask him something, his punch came first," Kim told the AP. "He told me to use my mouth only for eating and smoking. He said I shouldn't question things and should be thankful because he fed me and gave me lodging and work."

It was just as bad for the other slave, Chae Min-sik, a tiny man whose disabilities are so severe that he struggles even with basic words.

Only a week after his first capture, Kim began to plan another escape.

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"Angel Islands," the regional tourist board calls the 1,004 islands clustered in the sun-sparkling waters off South Korea's southwestern tip, because the Korean word for "1,004" sounds like the word for "angel."

Local media call them "Slave Islands."

Parts of the region have been shut out from the country's recent meteoric development. On many of the 72 inhabited islands, salt propels the economic engine, thanks to clean water, wide-open farmland and strong sunlight.

Sinan County has more than 850 salt farms that produce two-thirds of South Korea's sea salt. To make money, however, farmers need labor, lots of it and cheap. Around half of Sinui Island's 2,200 people work in salt farming, according to a county website and officials.

Even with pay, the work is hard.

Large farms in Europe can harvest salt once or twice a year with machines. But smaller Korean farms rely on daily manpower to wring salt from seawater.

Workers manage a complex network of waterways, hoses and storage areas. When the salt forms, they drain the fields, rake the salt into mounds, clean it and bag it. The process typically takes 25 days.

Sinan salt, which costs about three times more than refined salt, is coveted in South Korea, found in fancy department stores and given as wedding gifts.

"Everyone makes money from the farms," said Choi Young-shim, the owner of a fish restaurant in Mokpo, the southern port city that's the gateway to the salt islands.

Not everyone.

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The second time they ran, Kim and Chae again tried to find their way to the port. But they had to pass the grocery store to get there, and again the store owner's son, identified by officials only as Yoon, rounded them up and called Hong.

After another beating, it was back to work. The few hours they weren't in the fields, they slept in a concrete storage building filled with piles of junk and large orange sacks of rice.

Kim despaired of ever escaping. Hong was an influential man, a former village head. He was linked by regular social contact and family ties with other salt farmers and villagers, some of whom volunteered to patrol the island for escaped workers.

Although Kim lived only 3 kilometers from a police station, he never thought about asking for help. He believed he'd be ignored or, worse, returned.

Kim ran again at the end of the month. Hong quickly called members of the volunteer patrol, and, again, Yoon spotted the slaves as they tried to reach the port and bought them to Hong.

Furious, the owner issued an ultimatum: Run again, and you'll get a knife in the stomach.

Hong beat Kim so badly he broke Kim's glasses, leaving him nearly blind. He worked Kim so hard the slave was too tired to think about escape, even if he hadn't been terrified to try.

"It just drove me deeper into despair," Kim said. "I never had a chance."

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The exact number of people enslaved on the islands is difficult to determine for the same reasons that slavery lingers: the transient nature of the work, the remoteness of the farms and the closeness — and often hostility — of the island communities.

"It's like a game of hide-and-seek," said Park Su-in, an activist. "What we are finding is just the tip of the iceberg. It's hard to comprehend how bad it is for the disabled people who are forced to work out on these isolated islands."

Activists believe many slaves have yet to be found, as some salt farm owners sent victims away or hid them from investigators. They say others coached disabled workers about what they should say in interviews.

While island police officers were moved to different posts on the mainland as part of annual personnel changes, authorities found no collusion, according to a Mokpo police official who spoke on condition of anonymity because of office rules.

"If the recent investigation was done properly, then pretty much everyone on the island should've been taken to the police station and charged," said Kim Kang-won, another activist who participated in the recent investigation on Sinui. "The whole village knew about it. The local government office, and the police as well. It is clear negligence. And the problem hasn't been resolved yet."

Provincial police vowed to inspect farms and interview workers regularly. Choi Byung-dai, a police officer on Sinui Island when Kim was freed, expressed regret about Kim's treatment but also noted the difficulty of monitoring so many salt farms and a flood of seasonal workers.

Salt farmers blame illegal job agencies in Mokpo, which see mentally disabled workers as better bets because they're less likely to complain or run away.

"They're treated like dogs and pigs, but people in the community are used to it," said Kim Kyung-lae, a Mokpo cab driver who regularly drives local employment agents and disabled workers to the ferry port to meet with farm owners.

Others familiar with the island confirm that slavery is rampant.

A doctor who worked at the Sinui Island public health center from 2006 to 2007 said most of the workers he treated were abused or exploited.

"The police chief would tell me that I'd eventually come to understand that this was how things on the island worked," said Cho Yong-su. "For decades they'd exploited workers in this way, so they couldn't understand that this was abuse."

An outsider might cringe at what's happening on the island, said Han Bong-cheol, a pastor in Mokpo who lived on Sinui for 19 years until June. "But when you live there, many of these problems feel inevitable."

He sympathized with farmers forced to deal with disabled, incompetent workers whom he described as dirty and lazy. "They spend their leisure time eating snacks, drinking alcohol and smoking cigarettes. They are taken once or twice a year to Mokpo so they can buy sex. It's a painful reality, but it's a pain the island has long shared as a community," Han said.

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After a year and a half as a slave, Kim made one last bid for freedom.

He wrote a letter to his mother in Seoul that he never expected to be able to send, calling himself her "foolish" son.

He got a break when Hong's wife let him go alone for a haircut. Walking slowly without his glasses, he ducked into the post office and mailed the letter, which gave directions to the farm.

Kim's mother was stunned. She brought the letter to Seo Je-gong, a police captain for the Seoul Guro district. "A vanished person had suddenly reappeared," Seo, now retired, told AP.

Seo then hatched an extraordinary plan.

Because Kim's letter noted collaboration between local police and salt farm owners, Seo and another Seoul officer ran a clandestine operation without telling local officials.

Carrying fishing rods, they walked around like tourists who had come to fish and buy salt, and surreptitiously took photos of Hong's house and farm. After they watched Hong board a boat, they told Hong's wife they were Seoul police who had come to free Kim.

The officers found the slaves sitting on a mattress in the back room of a storage building with no heat or hot water. Kim wore thin, dirty clothes, slippers and socks with big holes. He looked, Seo said, like a person who had been homeless for a very long time.

Kim was frightened and baffled at first, then relieved. "I am going to live," he said.

When Seo took Kim to a local police station to give an official account, an indignant policeman asked, "Why didn't you leave this to us?"

Villagers, unaware that Kim's escorts were Seoul police, harassed him at the docks, asking where he was going. Some even called Hong.

When Kim met his mother the next day, they both wept. She stroked her son's face. "Everything is all right because you've come back alive," she says in a police video of their reunion.

Chae initially refused to leave Sinui. After Seo later found a 2008 missing person's report for Chae, police returned and rescued him. Chae, who'd spent five years as a slave, now lives in a Seoul shelter.

Hong was convicted of employing a trafficked person, aggravated confinement, habitual violence and violating labor laws. Yoon, the man who captured Kim and Chae three times, was fined $7,500. Two illegal job brokers hired by Hong to procure workers are appealing prison sentences of 2 years and 2 ½ years.

Kim, who lives in Seoul and occasionally works construction jobs, still seems amazed that his escape plan worked. He settled with Hong for about $35,000 in unpaid wages, but is furious that Hong is appealing his prison term next week. Kim will face him in court, and has been preparing for the moment.

His body aches, and he gets treatment for lingering pain in his neck, legs and spine.

"Now all I want is peace," Kim said. "I still get nightmares, still wake up in the middle of the night."

His time as a slave has even changed the way he feels about salt. He gets flustered when he talks about it, disgusted when he sees it.

"Just thinking about it makes me grind my teeth."

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Foster Klug is AP's Seoul bureau chief. Follow him on Twitter at twitter/apklug