Ku made her official debut at the 2000 Summer Olympics in Sydney, where she competed as a member of the South Korean squad in the women's volleyball tournament. Collecting a total of three triumphs, two losses, and eight classification points in the preliminary pool, the South Koreans lost the quarterfinal match to the U.S. squad, led by Kerri Walsh (who later turned into a beach volleyball player in the next three Olympics), with a five-score set of 24–26, 25–17, 23–25, 27–25, 14–16. During the fifth round of the match, Ku returned a ball down the left line that was called out and ended into a protest against the aggressive Americans. After suffering a heavy defeat in the quarterfinals, the South Korean squad finished eighth in a classification round match against Croatia with a set score of 1–3.