GACKT Official Weibo update. Translation below:

上弦の月〜最終章〜(2003)
17.birdcage

This is the ending song for MOONCHILD. It’s about the feelings of the protagonist whose fate is akin to that of being imprisoned in a birdcage. During the LIVE, this performance is pretty beautiful too, with the protagonist stuck in his distress, his memories from his youth, and the reality that he is unable to escape from, it is also quite mournful.
Enjoy it.

Source: GACKT WEIBO

Translation: GACKT ITALIA Team

Translation © GACKT ITALIA