Alright this is my favourite anime of all time, obviously a big statement to start a review with. I obviously don't expect anyone else to think so highly of the series, but I genuinely do think it is a masterpiece. I also don't like breaking anime down by how MAL does reviews numerically, but eh I'll give it a go.
This is a fast-paced anime, it's a 12 episode original. Keep that in mind, personally I think the pacing is well done. Every episode has its own direction in terms of what it wants to do if that makes sense, but it's still under one
story. The story itself looks simple during the first episode, but all I'll say is that there's A LOT more to it. Many philosophical concepts explored in the story, which I won't get into but if you go into the story with a philosophical lens you'll find a surprisingly high amount of stuff for 12 episodes. There are some central themes that are well-focused and explored throughout the run of the anime, and we get good conclusions to them when needed and others are left more open-ended when that is appropriate.
I'm not gonna act like it's some Ufotable or Bones stuff because it's not, but the art is still well-done. There are basically two main distinct art styles in Deca-Dence, and it throws some people off, think of Mob Psycho 100 or Masaaki Yuasa works. But the animation itself is pretty damn well done, has really great aerial combat(this is from the same studio who made Tanya the Evil for context), and transitions between the two styles damn well. The directing is also fantastic; episode 5, 8, and 10 stand out a ton in this regard.
I don't like talking about something as obviously subjective as music/sound in an analytical sense, but I'll say that the soundtrack was awesome and used very well, with many memorable tracks(especially the ED wowie). Voice acting was on point, and sound effects were well done. I don't have any flaws with it, fantastic job. Also Koyasu Takehito has a big role doing what he does best, sounding evil. Can't go wrong with that.
Our two main characters of Natsume and Kaburagi are FANTASTIC, and definitely carry in this department. They have a wonderful relationship that I can best describe as a shared inspiration. Both of our characters develop tons both due to each other and their general environment, and it feels very genuine. Natsume in particular has some moments that absolutely blew me away. The rest of our cast are obviously not as explored since this is a short anime, but some such as Minato and Fei bring interesting perspectives and make for some great dialogue. Our antagonistic force is also very well done with reason to their actions, and we come to a quite fitting resolution.
I seriously still can't believe how much this anime appealed to me. Obviously the enjoyment rating can vary person by person, as can honestly any of the other ratings. I've literally cried just from thinking of how much I love this anime, on more occasions than I can count. Episode 5, 7, and 10 are literally my three favourite anime episodes of all time. The anime also made me laugh a bunch of times, it's certainly good at being goofy when it wants to be. So yeah, I enjoyed it a ton. If you're super stuck up about me rating enjoyment as a 11, then just think of it as a 10 doesn't make a difference for me. Fantastic anime regardless :)