I heard a good bit about defections from North Korea but today was the first time I read about people decring to North Korea. Here is an interesting read about the life of one of seven U.S. soldiers to defect after the Korean War. Jenkins deserted in 1965 by crossing the DMZ expecting to the fairly quickly handed over to the Soviets and then included in a prisoner exchange back to the US. Instead, the North Koreans kept him, tortured him, turned him into a movie star (playing evil Americans) and married him to an abducted Japanese nurse. In 2005, he left (or was allowed to leave) to Japan and lived there until his death in 2017.
The articles about the other defectors are also a decent read. I found the life of James Desnok particularly interesting who seems to have quickly become a convinced regime supporter (and whose two sons are serving in the North Korean army).
This also happened during the Korean War itself. When the Korean Armistice Agreement was negotiated in 1953, the UN forces insisted on a provision in the prisoner exchange procedures that the POWs could choose which side to be repatriated to, free from repercussions. The Americans meant for this to be used to allow North Koreans imprisoned in South Korea to choose to remain in South Korea, and then did surprise pikachu face when dozens of American soldiers refused repatriation and chose to remain in North Korea.