I was told that this film thems song is chinese version of Secet sung by Denise Ho but actually it is sung by Ayu and this chinese version might be just optional.
This is a preview I found in their website wich has Ayu's Secret song.
http://www.confession-of-pain.com/index.php
Click the line which has "MV" .
And I also heard that Ayu will write an English lyrics for the song too