After joining Warner Music Group in 2003, Sit first plugged her debut song "XBF" and "Madonna's Kiss", catching attention from audiences. Sit released her first album "F Debut" on 8 April 2004. It became a best-seller in Hong Kong, being certified gold for sales in excess of 25,000 copies. The album contained the hit ballad "XBF" (short for ex-boyfriend) and another hit "Keanu Reeves Reply". The song "Keanu Reeves Reply" reached No. 1 in the charts of the four TV and radio stations.