All good, you have a flowing, balanced style.

My favourites are definitely 'Boss Battle', 'Ares', and first 'Solitary'.

Ooohh, Gackt and Yami no Matsuei! That's happy. I recently rewatched the series, so I'm totally tripping on the two of them right now and was happy to see this. I've always believed "Doomsday" was a particularly Muraki-ish song, so. . . .

I like how you've captured feelings so well. Could almost be called Impressions in that way. I think my favorite is the one from Tatsumi's perspective (I'm guessing); it captures his thought process so eloquently with so few words.

The last one, though, that sounds like the prologue to a much longer fic. Depending on how you take it, that is. I mean, it could be Surgatanus or Focalor or Yatonokami, or it could be something much worse that came out of a wormhole where the story left off. A good way to end it because it takes me as a reader in a whole 'nother direction, and now I want more of what that evilness is and what its next steps will be. And which of our very powerful characters is its target, for that matter. Well done.