Bitter-sweet Song

 is a track in Xenosaga II to III: A Missing Year. It uses the same melody as the Xenosaga II opening theme and Sweet Song (Xenosaga II ending theme) (and, by extension, Sakura (theme-piano ver.) and its remixes). Despite its name, it is unrelated to bitter.

It plays in Chapter 1 when Shion narrates how she first learnt of Almadel.