ACCA: 13-ku Kansatsu-ka is a quirky political drama, which moves at a slow pace that may turn off the more action-oriented viewers. In the long-run, it's this same slow pacing that helps the show accomplish what it did. The setting is strange and it has a lot going on, so the calming atmosphere helps all of these details sink in gradually and easily. The dense, dialogue-heavy plot is also easier to digest with this measured method of storytelling.
The main protagonist, Jean Otus, is a likeable character right out of the gate. He is rather indifferent about most things and is content with his current life, including his tedious government job. Nontheless, he gets pulled into the coup d'etat scheme and he plays along with it, despite not really caring. Even with all of his neutrality and complacency, he somehow comes out the other end as a cool badass. He is quite confusing in this way: at times he seems like he knows more than he lets on, while other times you wonder if he's not just the most oblivious character in existence. Either way, he remains an endearing character who is easy to root for.
Jean's relationships with his younger sister Lotta and his best friend Nino are surprisingly real. There is an unspoken trust and loyalty between the three, with almost a "no questions asked" policy that they abide by without issue. This trust and friendship is portrayed in a very down-to-earth way, with very little cheesiness. They all act like the mature adults they are, which is refreshing after having watched so many anime about immature teenagers who don't know how to communicate.
Despite the quiet feeling of the anime, it has a few plot twists here and there and the reveals are still able to pack a punch, maybe even moreso than they would have if ACCA had been a dramatic adrenaline rush. One reveal in particular is played out in such a nonchalant way that it took a few minutes to realize the gravity of what had just been said, and when it hit, it hit hard. ACCA is able to accomplish this because it has mastered the method of telling the viewers just enough to understand what's going on, while also keeping you just enough in the dark. This creates a sense of intrigue without too much confusion, and makes the plot twists very understandable in hindsight.
The calm, mysterious ambience is aided by the jazzy soundtrack, the fluid animation, and the attractive character designs. The aesthetic ties everything together, solidifying ACCA as a mature, thoughtful, and delicately executed anime, the kind that only seems to appear every once and a while. The one disappointing thing about ACCA is the lackluster ending. Without giving away too much, the conclusion essentially makes it feel as if nothing has happened, an unfortunate note on which to end a pleasant experience. Still, I highly recommend this anime to anyone looking for a good slow-burn drama.