One police officer in Seoul said, "In the past, missing persons reports usually involved children or senior citizens, but these days we see a lot of young people running away from home when they can't find jobs."

According to the National Police Agency, the number of missing persons reports involving people between 18 and 39 rose from 31,414 in 2014 to 34,710 in 2016. But reports involving minors fell from 21,591 to 19,870.

Police are usually stumped when they are asked to find missing adults. The law only requires them to investigate missing minors, handicapped people and senior citizens with dementia.

Adults who suddenly disappear are not classified as missing but as runaways, and police are not allowed to conduct search operations or check DNA samples since everyone is entitled to come and go as they please. Even if missing adults are found, police are not allowed to contact their family if the person does not want it.

But some desperate young people commit suicide or take to a life of crime. One runaway in his 20s was arrested after setting fire to three motels when he grew frustrated looking for jobs. "I couldn't even find a job, while my debts kept mounting, so I thought I'd be better off in jail," he said.

"People who run away from home because they have a tough time finding work are under a lot of financial and psychological pressure," says Lee Woong-hyuk at Konkuk University. "They are less likely than other runaways to come back home and are at higher risk of committing crimes."