In March 1970, a cadre from the Japanese Red Army hijacked a Japan Airlines plane, which they planned to fly to Cuba, via Pyongyang. But the North Koreans refused to let them go. Forty four years on, they're still there.
It is not certainly the first time that journalists and others have visited the aging hijackers in North Korea. Over the years many have visited and interviewed the former revolutionaries at their complex, which was quite a luxury facility even by Japanese standards, fitted with staff and expensive cars. However, this was as much to keep the Japanese under lock and key as provide them with earthly comforts. At least one of the hijackers and his wife is suspected of dying in an escape attempt.
I take that to mean they were killed while trying to escape. The article hints that the group were repurposed for Pyongyang's kidnap to order targeting of Japanese citizens in the 1970s and 1980s.