The story seemed to be simplistic at first, following a series of mysterious attacks that are somehow related, but soon it gets clear that that's just the tip of the iceberg. The anime does a lot of sidetracking in an effort to portray and deepen different sizes of the same story. You get to see various distinct perspectives and each one is unique. Because of that, at some points, the storyline felt disconnected and too steady as things wouldn't actually progress in any way and you'd watch entire episodes just showing the reaction of newly-introduced characters to the main plot, which are mainly represented through unconventional ways, such as metaphors and visual analogies.
That added beyond what I think was necessary to the mystery of the story by the cost of slowing the pace of the series. Later on, it gets clear that's the intention of the director. You end up realizing this anime isn't meant to create a really mysterious atmosphere and stimulate the viewer to theorize and try to guess things like "who's the culprid?", but instead, to represent how collective imagination shapes individual's perception of reality. The plot was unpredictable, which is great since this genre tends to be very unoriginal but on the other hand, it used too much fantasy, so I wouldn't actually call it a very intelligent plot, but a creative one... It's a good thing it escaped from clichés, though.
Other unconventional thing about this narrative style was that there was no protagonist. Each episode has actually one character that got more attention than others but that was rotative. Stories about mysteries that seek to create a suspense atmosphere (which isn't the proposal of Mousou Dairinin) benefits from the addition of a strong character, making people care more about what's happening due to this charism link. The lack of a fixed protagonist, although compatible with the chosen narrative style, made the story lose personality.
Artstyle is nice, although it's sometimes inconsistent. The anime abuses of exaggerations and grimaces to portray distorted characters, while others are just 'normal'. This is not a downside, though, as the anime uses this inconsistency even on scenarios when it's convenient, in a very creative choice. Sound is ok but the op is one of the most annoying I've ever heard...
At the end, Mousou Dairinin is an unique anime, it has an unpredictable and creative mystery story, but is too unconventional to be broadly recommended. I personally appreciate how original and creative the anime is, but at the same point, I struggled to care about the story, since it's focused more on social criticism than mystery or suspense... It's an intelligent anime and it sure deserves praising, but it's not very accessible and the only reason I didn't score it higher was because it didn't appeal to my personal taste, but whoever is into dense thought-provoking stories might love it.
