ANSAN, South Korea — Few North Koreans have sought South Korean citizenship as long and as doggedly as Kim Seok-cheol.

Since a famine hit their totalitarian homeland in the mid-1990s, more than 30,000 North Koreans have defected to South Korea, most of them fleeing through China. Mr. Kim, 52, fled North Korea much earlier — in 1984 — and even helped other North Koreans trapped in China get safe passage to South Korea, lending them money and helping them find smugglers who could take them.

But Mr. Kim’s case is noteworthy because he has been in legal limbo for decades, ever since fleeing to China at age 19 and adopting fake Chinese citizenship papers that he said he used, along with bribes, to avoid being deported back to North Korea.

Although he has lived in China for most of the last three decades and married an ethnic Korean woman there, Mr. Kim says he never felt at home or safe there and has longed to defect to South Korea.