 In 2006, she released the track "Sarang Ga" ("Love Story"), which became the title song of "Pure in Heart".In 2012, Ku released her first self-composed soundtrack, titled "Fly Again" for SBS's "Take Care of Us, Captain", which she stars in.Ku released her first album "Breath" in 2009, an album of new-age music which included her composed song for her friend and singer, Gummy, entitled "Around the Alley".