[Illidan]

Note that the other two performers aren't credited in the booklet (or anywhere else I looked), but they are actually singing a couple of lines of the first song.
In the booklet scan, they have different colors in the lyrics: Misato Tachibana (CV. Chika Horikawa) sings the green lines, Koujirou Sasahara (CV. Yoshihisa Kawahara) the teal ones, and both the purple one.