Fantastically dark idea. It's a little less dark in execution, but still twisted enough to be capable of making you swear at the screen. I enjoyed it.
Myoujou Academy sometimes has a Class Black. As far as the rest of the world is concerned, this contains thirteen schoolgirls. In fact, it contains twelve professional assassins and one target. It's a competition! The rules are as follows. Failure or breaking a rule means expulsion, both from the game and from the school.
1. No outsiders must learn the truth or get killed, including the class's teacher (who knows nothing and thinks he's teaching ordinary schoolgirls).
2. You must announce your assassination attempt by getting a notification announcement to your target, after which you have 48 hours to do the job. You don't have to sign the notification, though. The target won't know that her enemy is you, unless of course you choose to tell her.
3. The winner gets whatever they want. One wish, granted. (There's no magic involved and you couldn't wish for a time machine or anything like that, but the organisation running Class Black appears to be at least as rich and powerful as the government of any major Western country.)
This year, they include an emotionless cold-as-ice protagonist, a serial killer, a poisoner, a girl with a split personality (timid vs. psycho) and a sneering bitch who I thought of as "the one with the bad personality" even by the standards of Class Black. These are not nice people. Twelve of the class are like that. The thirteenth, though, is the gentle, optimistic Haru Ichinose who's kind to everyone even if they're telling her to drop dead and just wants everyone to be friends. Oh dear.
What's interesting is that there's an obvious route for this story, but the anime avoids it. If you think about it, it's in everyone's interests to protect the target. The game can only have one winner, after all. The timing of your assassination announcement could thus be quite a difficult problem. Come forward too early and you'll have a full class of rivals trying to stop you, but leave it too late and it's all over.
You could have a lot of fun with that premise, but at the same time I think it would be a little more generic than this show. It would be a variant on Battle Royale, basically. This show, on the other hand, has that cold-as-ice protagonist (Tokaku) deciding very early that she's going to break the rules and become the target's bodyguard. There will be one occasion when one assassin takes out another just to reduce the competition and keep the target (temporarily) alive, but broadly speaking the girls here don't seem to give a damn about each other's murder attempts. If X is trying to kill Y, then A, B and C will just sit on the sidelines and avoid getting involved. It's basically Tokaku + target vs. The Latest Assassin(s), with no help to be expected from anyone else.
(I say Assassin(s) because there's no rule against attempts overlapping. Bad news squared.)
Comparisons with the original manga sound interesting. That's still ongoing and so little of it had come out at the time that the anime was less than halfway through when it caught up with the manga. This happens a lot, but on this occasion they'd been given an outline for all the chapters that hadn't been written yet. The manga and anime are thus broadly in tune with each other, but I understand that the manga has more fleshed-out characters and more overt lesbian subtext.
How dark is this show? Well, the idea is horrific. Some of the backstories are gut-wrenching and the cast includes some utter monsters. However you'll notice after a while that the show's oddly reluctant to kill them. After that, the finale includes a backpedalling, while the 13th OVA episode is a fluffy romp that could almost be seen as a parody of the series. It involves an island, fanservice and amusingly rubbish weapons (e.g. water pistols).
That said, though, one of the episodes ends in a double suicide. There's torture and threatened eye trauma. Some of the girls are terrifying and the last couple of real episodes (i.e. ignoring the OVA) include revelations and twists that are genuinely shocking. A certain person I can't name because of spoilers is sick in the head. She needs help. What she decides is wrong on a level that wouldn't even have occurred to me.
Then there's the ambiguous departure of the losing assassins. They'll fail in their murder attempts and then never be seen again. Supposedly they've been expelled, but flowers get left on desks in a very memorial-like way and we've no indication at the time of whether or not what we've been told is what's really happened.
I think it's good. I'd recommend it. Tokaku is a walking ice block with the emotional range of a teaspoon, but the target she's defending couldn't be kinder and gentler, so as a partnership they're balanced. I like the fact that it doesn't take the more obvious road, since in the end the show has a solid rationale for its choices and everything's for a reason. I think the use of Romeo and Juliet in eps.5-6 is clever, since that's a play with poison and revenge killings as well as the love for which it's more famous. Similarly, trying to befriend even attacking assassins is more rational than it looks, offering as it does the chance of both staying alive and gaining an invaluable ally. Hey, it worked with Tokaku.
It's not as dark as it could have been, but had it never pulled back from its darkest extremes, then we'd have had a show to shred our souls. Lots of evil. Good stuff.
"One day, I'll follow you. Please wait for me there." (Spoken to the deceased.)