Darkness ~Yami no Yuusha~
Oh hey, Nero has his own song? Some parts are okay, but overall I don't like it. Nice touch having the Shadow Line sing though.
A Hikari theme song? Yes! We hear part of it in the background of one ep, but it's nice to hear the full thing. It's upbeat, but also really quietly passionate, which fits his character.
I surprisingly liked this song. I thought it'd be way oversexualized or annoying, but it's quite a cute song. Way to go Horie Yui.
Blue Lens no Mukou e
I was surprised by Tokacchi's song. I'm not familiar with his singing voice, and he sounds fairly masculine in this. Of course, now that I know it's him, I can totally hear his character in this.
Mio's singing voice is really high. It's a little catchy. One interesting thing to note is that the lyrics were written by Riria, Mio's actress.
Sanjou! Narikiri GIRL
Unfortunately, I couldn't really get into this song. It's too bad, since I do like Kagura.
Noire Noire Nooire
Hisakawa Aya is a voice acting pro, and it shows here. (Sailor Mercury, Cure Moonlight and a million other roles.) I actually didn't think I liked this song at first, but after repeat listens, I can really admire how much range she has. There's something about the timber of her voice that's so, I dunno, maybe sexual? While not an overly sexual character, she's definitely extremely feminine. She's both a mother and a stereotype of a noble woman.
Ankoku no Arika
If Noire is a song that makes use of femininity, then Ankoku no Arika makes use of the Emperor's masculinity. Ohkuchi Kengo does a great job with this song. There's definitely a touch of loneliness and sadness in the song that's befitting his character.
Unfortunately, the other songs really didn't stick with me.