From the pov of somebody who never read the manga or even heard about this story until the anime, I'm very disappointed in it. I went in with an open mind but it just got worse and worse.
I really enjoyed the animation style and pacing, the way they use flashback scenes and cuts was done well, the voice acting was fine to me. I was ready to dive into this fantastical plot when I started noticing some pretty sick stuff.
Spoilers!:
I love when a show uses sex and nudity in a tasteful, thoughtfully done way, but this show does neither. They always showing women in sexual situations in a gratuitous fashion and it doesn't add to the storyline. There are scenes of women (background characters so not even relevant to the plot) having sex/masturbating that's clearly only for the male gaze. Every scene with Miko running shows her chest bouncing, which is incredibly unrealistic for a runner, and is just sad to see that somebody actively wanted to include this in the show.
The final straw was when Akira raped Silene during their fight scene. Even if we are to believe that's his demonic side taking over, the way the rape is portrayed, with epic music and an intense monologue about him defeating her, has a positive "I am stronger than you" connotation. This show had a lot of potential to reach a wide audience but they just shot themselves in the foot.