A native of Seoul, Ko was elementary schoolmates with future Sechs Kies bandmate Kang Sung-hun and g.o.d member Son Ho-young.
Ko was recruited by Kang to join the boy band he and his high school friend Eun Ji-won were forming.
[6] Unlike other members, he did not continue his career as a solo singer but he was cast as a host in an internet broadcast and as an actor in a television drama.
[8] In 2008, fellow Sechs Kies member and leader Eun Ji-won appeared in the entertainment program Come to Play and remarked that he had not seen Ko since the group's disbandment.
[12] Ko, who had left the entertainment business permanently after the disbandment to pursue a new career, surprised the members of SechsKies as well as all the fans by appearing at the reunion concert and performing their hit song "Couple".
On July 18, Ko publicly appeared as a sponsor for a charity basketball event and held interviews with the media for the first time in 16 years.