Kim Ryon Hui is one of them. The Pyongyang dressmaker -- turned North Korean defector -- says she is trapped in South Korea and desperate to return to her family.
Before defecting in 2011, Kim lived a relatively upscale life by North Korean standards. Her husband is a doctor and the family recently received a new, larger apartment from the government.
Kim in South Korea and her family in North Korea spoke to CNN about her case.
Kim went to China four years ago to visit relatives and seek medical care for liver disease.
She had been hospitalized for six months in North Korea and had heard China may have more advanced treatment. She assumed it would be free of charge, as it is in North Korea, where the state covers most expenses including housing, healthcare, and higher education.
But once in China, Kim soon found she couldn't afford the staggering medical bills. "It became a huge burden for me to go through treatment in that situation. I couldn't ask my cousin for money," she told CNN.
Kim says she began working at a restaurant in Shenyang but the low wages were not nearly enough to pay for her expensive treatment. She says the Chinese doctors wanted cash up front.
"A broker told me that Chinese people go to South Korea and earn a lot of money. The broker's neighbor also did it for two months," she told CNN.
"I was thinking of recovering completely before returning to my aging parents. I wanted to return home in healthy state. So I said I will go to South Korea for two months and earn the money and get myself treated."
Smuggled into South Korea
She now calls that decision a horrible mistake.
Kim was taken with a group of other defectors to South Korea, but even before she got there, she says she was having second thoughts.
Kim says she didn't realize that once she signed papers renouncing her North Korean citizenship she could never go home.
"I told them that I didn't know this so I wanted to escape. But the broker took away my passport from me and refused to give it back," she says.
"Other defectors who were with me said if I go out and get caught they too will be handed over to China's Public Security and their life will be in jeopardy. Because I didn't have a passport, I had to follow them and I ended up in South Korea."
Kim says that, at the time, she didn't even know what a North Korean defector was.
As soon as she arrived in South Korea, Kim began demanding to go home to the North.
For South Korea, it's not that easy. It has a protocol to bring defectors in, but it is illegal for them to return.
No way home
And in order to be released from a South Korean processing center, Kim says she had to sign document renouncing communism and agreeing to follow the laws of the South. By doing so, she became a South Korean citizen.
Kim says she's tried to find a smuggler, made repeated calls to the North Korean consulate in Shenyang, -- and then took a desperate measure she now calls "foolish."
She says she pretended to be a North Korean spy in order to be deported. But South Korea doesn't deport spies, they imprison them.
So after turning herself into the police, Kim was sentenced to two years for passport fraud and espionage. Her sentence was suspended in April and she is now out on parole and under close watch. Her status as a convicted criminal makes travel out of South Korea legally impossible.
She told CNN: "There is nothing else for me to say but I am sorry. I didn't even imagine that I would create such a huge problem.
"The wrong choice that I made, my choice of wanting to earn money for my treatment, led to the worst situation in my life. I am regretting with my heart and I am so sorry that I've brought such suffering to my aging parents and husband and my daughter."
Kim says she is now stuck in South Korea with no more options, working as a machine operator at a recycling plant.
"I am living in Daegu and I am going through a regular treatment in a hospital there," she says.
Although her health has improved, Kim says the mental anguish is unbearable. Her arms bear the scars of multiple suicide attempts.
Messages across the border
In Pyongyang, we met Kim's husband and 21-year-old daughter, who hasn't seen her mom since she was 17.
"Why? Why can't she come back," asks her sobbing daughter Ri Gyon Gum. "Why do we have to go through such suffering?
"Why do they drag her like this, despite how she says she wants to go back, [why] not let her go? She has her family, husband and daughter in her country, a daughter who misses her mother, a husband who misses his wife. Do they not have heart and blood?"
Asked if they'd like to send Kim a message, her husband, Ri Gum Ryong, speaks to the camera, at times bursting into tears.
"To my wife in South Korea, don't forget here you have parents, a husband and daughter, and a socialist nation. Keep on fighting until the end," he says.
"My wife is fighting until the end right now, my whole family, my whole North Korean nation. We will all get together so that she can come back. Never stop the fighting."
In South Korea, Kim's hand covers her mouth when she sees their video message, as she sobs violently and watches the clip playing on the computer screen.
It's the first time she's seen her family in four years.
"How can this be? What am I going to do," she asks.
Kim records a tearful apology to her family, telling them doctors are treating her, saying she's never forgotten them or her country, and promising to do everything she can to come home.
"I will return. At some point I will return. Please wait for me until I return," Kim says.
South Korea's Unification Ministry says the law does not allow them to bring Kim's family back together.
Like so many others on the divided Korean Peninsula, they are suffering the anguish of separation caused by decades of hostility between North and South, one of thousands of families torn apart.
We meet once again with Kim's husband and daughter in Pyongyang, to show them her message, which they promise to pass on to her aging parents. They remain unsure when, or if, they'll ever be reunited.
As the video begins, Kim's daughter's hand covers her mouth in the exact same manner as her mother. They bear a striking resemblance. Mother on screen, daughter watching, both sobbing violently.
There are no words. Only heartbreak.