Ji was born on April 3, 1982, not far from the Hoeryong concentration camp,[4] and grew up during the North Korean famine of the mid-1990s.

[5] "The family survived by eating the ground-up cores of corn husks and the roots of cabbages", according to one report.

Ji later said, "There was no meat and never any oil....Sometimes we could get seaweed and we would also eat mountain grasses....At harvest time, rats in the field would stash seeds down their burrows, which we would dig up.

He later recalled regaining consciousness and seeing the rear of the train receding down the track and then realizing it had run over his body.

"[7] His father had been a devoted member of the ruling North Korean Workers' Party, but the accident and its aftermath changed his views.

"When my father came to see me after the accident happened", Ji later told The Guardian, "he finally realized that it was more important to save his family rather than the party.

"[5] For ten months, "his father nursed him back to health primarily by feeding him a little bit more food than usual, which he got by lessening the rations allocated for the other family members.

"[6] At one point Ji crossed the border into China in search of food; on his return, he was arrested and tortured and his crutches were taken from him.

[8] This event, he related, was the main motivation for his desire to leave North Korea and relocate to another nation.

He had founded a group called Now Action & Unity for NK Human Rights (NAUH), which "raises awareness of North Korean human-rights abuses and has paid for defectors to move from China to South Korea".

The group's members "hold street campaigns during weekends in Seoul, unfurling banners and giving out leaflets, and organise lectures".

Saying that North Koreans "weren't brainwashed to worship Kim Jong-un", he said, "I expect the third generation of the dictatorship will not last long because of that fact."

[9] A May 2012 report described Ji as a law student and stated that he held a silent demonstration against North Korea every week.

[10] In April 2015, he said that his favorite part of the recently released film The Interview, a comedy in which Kim Jong Un is murdered, was when Sook, a North Korean interpreter played by Diana Bang, turns against the regime.

[full citation needed] Ji went on to describe that even after successfully escaping North Korea, many defectors face a "psychological longing for their family members".

On August 14, 2024, Ji was appointed as the governor of North Hamgyong province, which was a vice-minister level position under the Ministry of the Interior and Safety.

"[3] December 2014 articles in the British press cited Ji and other defectors to the effect that North Korea was "systematically purging its disabled population by making them disappear from public sight, subjecting them to chemical weapons tests and castrating them".

He said that two other defectors had "told him of a village in a remote mountain region that had been effectively turned into an asylum to house people with dwarfism".

He made the argument that a majority of North Korean defectors are in vulnerable groups, stating that Sae-byeok's story is a realistic one.