I have a nasty feeling that this anime might have killed its parent novel series, although that's pure speculation. When a light novel series gets an anime, that's usually for the sake of being a twelve-episode advertisement, basically. If it's successful, new fans buy the source material and everyone wins. If it bombs, sometimes this gets the original novels cancelled. That's not always very fair (e.g. good books got hammered by a bad adaptation), but that's how the business works.
This anime aired in April-June 2017, while the original light novels ran from February 2014 to December 2017. That's a bit worrying, although I know nothing about the behind-the-scenes story. All this is guesswork. Furthermore, the anime has some features that are pretty much guaranteed to wrong-foot an audience (including me), although I personally liked the show a lot and I'd have been delighted to see a second season.
Ah, no. Maybe I'm wrong. Two spin-off manga series are still ongoing. That makes me more hopeful.
It's set in a fantasy world inspired by medieval witch hunts. In this world, witches are real and they get burned at the stake. This might be surprising given their power levels (i.e. they can cast magic), which made me think that had magic been real in medieval times, all those witch-hunters would have got turned to toads. Here, though, it's more complicated. There are rival magic-using groups and the dilemma of whether it would be right for a witch to use her powers to save herself. If saving your own life made ordinary people even more scared of witches, wouldn't that just make the hatred and the witch-hunts more intense for everyone else?
Our hero is a huge, misanthropic mercenary who carries a sword that's bigger than you are, plus a collection of knives and mini-bombs. (The main difference between him and Guts from Berserk is that our hero here is secretly kind when you get to know him. Guts just gets scarier.) We never even learn his name. He's just "Mercenary". He's also endured a life of bigotry and racial discrimination, because he's a Beastfallen and so is likely to have both humans and witches trying to kill him for money. If you try to befriend him, he'll push you away. Sounds grim, right? Well...
DISCONCERTING ASPECT #1: he's a big Disney furry thing. He looks like he's walked off a movie with singing teapots.
I got over that, but it still made me blink.
His ally-to-be is Zero, a witch. This makes him hate her, but Zero doesn't mind that. Zero's the most confident person in the world, probably because she might also be its most powerful magic-user. She talks in Ye Olde Archaic, she orders everyone around (including Mercenary) and she's entirely unbothered by not knowing how the world works. As far as she's concerned, she's always right and everyone else is inferior. However that's because she was born in a cave and spent almost all her life in it, while in addition she's devoted herself to a mission to save the world. She wrote a book. (It's the Grimoire of Zero, obviously.) Her aim was to disseminate magical knowledge and make the world better, but unfortunately the book got stolen (bloodily) and the only outcomes are war and ethnic cleansing.
The Zero-Mercenary relationship is at the heart of this story. It's rather lovely. They're both very nice, underneath. Zero's effectively proposing marriage as early as ep.4. It's platonic and technically just a witch-servant arrangement, but Zero clearly thinks very highly of Mercenary and wants to stay with him permanently. Meanwhile Mercenary keeps trying to act grumpy and embittered, but it's still charming to see the two of them together. (Other party members will arrive, incidentally, but Zero and Mercenary are the core characters.)
Romance is ostensibly off the table. Mercenary's a grumpy, repressed man in the body of a beast, while Zero's age is unclear. She's an anime character. Who knows what she's meant to be? Is she a child, or just short? (She's tiny compared with Mercenary, but so is everyone.) There's what may or may not have been intended as a comedy lolicon character in a later episode or two, but then again we're told that witches live far longer than humans and that Zero's older than she looks. She's old enough to have written the most powerful magical book in the work, for starters. (She also has no modesty, whereas Mercenary's quite easily shocked. This can be funny.)
DISCONCERTING ASPECT #2: so it's an anime odd-couple show. Two funny characters travel around a magic fantasy world, having entertaining adventures and making you hope they get together permanently. Japan's full of anime like that... but then the series goes into sex slaves, massacres and entire villages being burned to death. (Admittedly the "sex slaves" are just a gag, but it's one that's accepted without question and even exempts you from paying tolls to get through the city border. Presumably that's a recognised thing, with your status as property meaning that you no longer count officially as a person.)
Apparently the original novels are pretty dark. The anime's been accused of cutting out serious and difficult scenes for the purposes of making a lighter, softer show... but even so, the show clearly turns serious well before the halfway point. People can hurt each other. "It's man who creates the monsters."
I like this. It's going to upset a certain segment of the audience, but I liked it a lot. My only problem with it is a possible lack of clarity in presenting quite a complex situation. There are at least three active magical factions in what's effectively a war: (a) the Sorcerors of Zero, who aren't led by Zero and indeed she objects to them quite a lot, (b) the rogue witches, (c) the kingdom's state sorceror who's leading the witch-burnings. That's not counting non-rogue witches (who exist and are just trying to keep their heads down and not get burned) and individual players like Zero herself. Alas, though, once they're out and fighting, it's not easy to tell the difference between two big bunches of magic-users. Were those (a) or (b)? Dunno. Does it matter? They're trouble and they can cast spells. I got by, but that's not ideal.
Then, what's more, the show changes again.
Nasty, realistic fantasies with dark themes are familiar, too, in their own way. People see violence, killing and a baddie and they set their expectations accordingly. Unfortunately the show then overturns that with yet another change of direction at the eleventh hour, with the ultimate threat in ep.12 being simply... people. The threat is the war itself. If people think they can win a war, suddenly events will start snowballing away from you and it no longer matters if you're a goodie or a baddie. Antagonists can turn out to be good people. The king's noble! He refuses to abandon civilians. He's a sincere man making decisions he believes to be right, but that makes the situation more powerful when what he's seeing is a once-in-a-lifetime chance to annihilate all witches.
"Goodies" vs. "baddies" is often the fodder of simplistic, fun stories. This series is exploring a society that can embrace racism and witch-burnings. That's what drives someone to pull almost the fantasy equivalent of an "Adrian Veidt in Watchmen" gambit.
I've seen reviewers saying of this, "It's unsatisfying, it feels forced, and it's just plain bad writing." Personally I disagree with this judgement (strongly), but I can't say that it's not a semi-deconstructive plot development and so, again, it won't be for all audiences.
On top of that, we have the stuff that genuinely doesn't work. The animation goes downhill a bit. There are some CGI crowds in the last few episodes that look obvious and cheap. More importantly, I disagree with the finale's logic. Would witch-burnings really disappear just because you'd got rid of the witches? Would a medieval society care about that? Burn someone! Burn the foreigners! Burn anyone who's a bit different from you! People got burned to death in Europe for being witches for centuries and I'm pretty sure the evidence for actual magic use was generally on the flimsy side. If you made magic disappear, how would ordinary people know? (Also, in a world where magic was real, I'm pretty sure medieval states would quickly harness it and use it as a weapon against each other. It would be an arms race. The best reason why that mightn't happen could be if the witches themselves had moral objections and/or were terrified of getting involved in all that.)
I liked this show a lot. It's a gnarly combination of very likeable but still rough-edged main characters in what becomes a pretty dark story. I like Zero and Mercenary a lot. I like the story they're in so much that I can forgive the stuff that needed explaining at the end. It's got idealism and goodness where you don't expect it, but not necessarily in a good way or leading to positive outcomes. Idealists might destroy the world, although admittedly they might also save it. I'm really hoping for a second season.