If I had to guess, the most important factor in making a show about assassins work is building a pervasive air of mystique. It seems plausible enough: the whole point of assassination is that no one quite figures out what happened, save for the one pulling the trigger, and maybe their targets for a few seconds before the trigger is pulled. Even when we're following the assassin, the only one who lives to know the full story, it's no fun if we're privy to all those details, and moreover starting with Noir—at least in anime's foray into assassin stories—there's an endless world of shadows that come with doing the most illegal job on the planet. Perhaps the most abnormal thing about the Noir assassin duo is that they aren't beholden to any government or syndicate, where in the real world most lone wolves would probably be picked up or picked off by bigger, more well-funded groups, the former of which director Mashimo Kouichi would experiment with later in Requiem for the Phantom, while the latter of which serves at the focal point of tension in Noir.
The syndicate in the shadows is something akin to the Knights Templar, a fraternity called Les Soldats who control the elections and power structures in dozens of countries while purporting to not even exist. Their opponents, a pair of female assassins, one a seasoned pedigree from Corsica, the other a Japanese schoolgirl missing both her memories and her remorse, working together under the ancient and sacred codename of Noir. Information about Les Soldats is revealed slowly, almost punishingly so, and for most of the show they come off more as a force of nature than a centralized group. As for Noir, we live day-to-day (or rather job-to-job) life alongside them in Paris, as they face setup jobs, Soldats agents, and of course moral quandaries in the line of duty. We know as much as they do, and between Yuumura Kirika's amnesia, Mireille Bouquet's desire to find and kill the people who took her parents' lives back in Corsica, and the details in their targets' lives left unsaid, we don't know a lot, even standing on the right side of the gun barrel.
Even on an episodic structure, the slow reveals of the world of Les Soldats keeps the atmosphere alive, and makes every episode feel like a possible turning point, sometimes even after the credits roll and nothing new was learned. For the early episodes the show rides the wave of novelty, with us fumbling in the dark without even knowing too much about Noir themselves. The palate is dimmer but with an emphasis on reds and other sunset colors, and the soundtrack, albeit repetitive, is classic Kajiura Yuki in the operatic vocals and orchestral instrumentation. Again, barring all other factors those episodes hit all the right notes for an assassin show, and a couple leads on the Soldats keep the episodes feeling worthwhile outside the individual plots.
Then, as the episodic structure starts to wear thin, the plot kicks into high gear. A few encounters with Mireille's extended family and hometown let Noir grab hold of the illusory organization for once, and we even start getting treated to views of the old men making the group's decisions from on high. The Soldats assassin Chloe starts to play a more ominous role, besides just being an overwhelmingly powerful yet childlike outside force, neither ally nor enemy. She starts to pull Kirika and Mireille apart, pulling Kirika towards a different path that doesn't seem to be wholly in line with the Soldats' agenda. The Knights Templar comparison starts to veer from just being a secret and powerful society, and tends more towards a supernatural religious cult. And while I was afraid of the scale blowing out of proportion, the result was sufficiently dramatic that I'm happy with the way things turned. More dramatic and removed from reality, for sure, but removed from reality in the way a mystery story should, in a quiet corner of the world frozen and isolated in time, with the future of the world distilled down to three assassins communicating through their knives and bullets.
There were two main scenes that stood out in the show. The first was the meeting between Kirika and Mireille, a shootout in a construction site that occupied half the first episode. Kirika's fluid takedowns of the operatives scattered around the building were arresting, and the framing was beautiful. One shot gave me nightmares the day I watched it; Kirika wrapped a cloth around her attacker's neck and then leapt off the building's edge, and even though he was the one strangled to death her body popping down from the floor above, her arm taut above her tilted neck all in silhouette against a sunset, she looked like the one being hanged. The second scene was actually a whole episode, when Kirika wakes up in a village that has been ready to die for her since long before she was born. The experience pushes her over the edge as an assassin, and signals the ending act of Noir. But it stood out to me because no setting better captured the feeling of everything being just a little bit off below the surface.