Volume 4 is the album of the chibi-senshi. Athene being a little limelight fan created her own band called 'Sakura'. The three chibis do love singing, especially Ariel, so they decided to create a niche and sing their own jpop songs. It isn't really attached to the main fic, just a flight of 'what if' fantasy and it just shows how easy it is these days to be a star. The songs are cool though, basically my personal favourite 'Happy' anime songs.