She was the 1991 World Champion on the uneven bars, winning the event with a perfect 10.0 score and a routine that included an original release move, the Counter-Kim.

While her real age was never ascertained, it was discovered that the Federation had submitted inconsistent birth year information for her at least three times at three separate international competitions.

She was expected to challenge for bars gold at the Barcelona Olympics in 1992, however, a step on her dismount kept her in fourth place (tied with two Romanians, Lavinia Miloşovici and Mirela Paşca), just out of the medals.

[8][9] It was eventually discovered that North Korean officials had falsified Kim's birth year at least three occasions, supplying different information at different competitions.

[9][1] By at least one estimate, she was no older than 11 or 12 when she competed at the 1989 World Championships,[1] and at the team portion of the 1992 Olympics, Béla Károlyi suggested she may have been as young as 10 at the time: he remarked, "Her milk teeth are falling out, which is a good indication she's not even 11.

[1] Kim, however, was permitted to keep the medals she had won in international events, including her 1991 World Championships gold, as she was determined to have no involvement or knowledge in the fraud.

[10] The same year, her country's government honored her by including her in a series of postage stamps commemorating North Korean world champion athletes.

The rationale behind this estimate is that the North Korean Federation was still supplying inconsistent birth dates for Kim in 1991 and 1992: if she had been born in 1976 or 1977, this would not have been necessary, as she would have been properly age-eligible for these events.