[2] 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.

[3][4] 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.

[6] At the 2004 Summer Olympics in Athens, Ku qualified for the second time as a member and captain of the South Korean squad in the women's volleyball tournament after receiving an automatic berth from the Asian Championships.

Unable to improve a fair performance from Sydney, she and the rest of the South Korean team were defeated in the quarterfinal match against Russia with a unanimous set score of 0–3 (17–25, 15–25, 22–25).