Born in Osaka, Japan, to a Japanese mother and a Korean father, Ko's birth date and Japanese name in Japanese official records are 26 June 1952 and Takada Hime, respectively. Her father, Ko Gyon-tek, worked in an Osaka sewing factory run by Japan's ministry of war. She, along with her family, moved to North Korea in May 1961 or in 1962 as part of a repatriation program. In the early 1970s, she began working as a dancer for the Mansudae Art Troupe in Pyongyang. Her younger sister Ko Yong-suk sought asylum from the U.S. embassy in Bern, Switzerland, while she was living there taking care of Kim Jong-un during his school days, according to South Korea's National Intelligence Service; U.S. officials arranged Ko Yong-suk's departure from the country without consulting South Korean officials.