This show can't be discussed without spoilers.

A killer commits lots of murders, one by one, without being caught. Some have found this entertaining, but I wanted the entire cast dead, especially the protagonist. However, the last few episodes improve.

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A pink-haired girl called Nana is murdering teenagers for the good of mankind. (They have superpowers. How many times have I seen that in comic books?) Her shadowy employers are clearly being economical with the truth (to put it kindly), but she's not clever enough to weigh this up rationally despite being superintelligent. In fairness, though, it's all too easy to believe in the show's description of the damage that was caused by arrogant idiots with superpowers.

Are her victims good people? Not usually, but sometimes they're okay and only dangerous in theory, one day, if no one takes their personality problems in hand. Does Nana care? No. Does she plan to kill everyone anyway, no matter what? Sure.

It's a dark show, obviously. All sorts of reactions to it are possible:

I disliked Nana a lot. Yes, sometimes she'll be killing people who deserve it, but does that mean I should care? She doesn't, after all. She just kills, lies, kills, deceives and kills some more. Theoretically, there's a certain level of interest in the fact that a unpowered killer is hunting down superpowered targets with her main weapon being her brains. That's a decent fight, especially when an equally intelligent classmate starts openly suspecting her.

It's worth comparing Nana with other cute, pink-haired psycho protagonists in shows like Future Diary and Happy Sugar Life. Them I like. They have relatable (if sometimes disturbing) goals. They just happen to be more flexible than most when it comes to overcoming human obstacles. Nana, on the other hand, is simply an assassin. Even when uncovering evidence of secrets she hadn't been told about, she doesn't care and just focuses on more killing.

"Should I have spared [SPOILER], had her [SPOILER] and tried to find out what happened on this island? Don't be stupid. I only need to carry out my mission."

Fundamentally, I just don't enjoy watching Nana kill people.

Well, yes. That's almost true. Her first two victims are decent people, but their superpowers and personality issues mean that they'd be potentially lethal one day. After that, though, Nana kills scumbags who conveniently reinforce the show's premise.

Personally, I don't get this at all, but hey. Nana often skates close to the line and there are lots of surreptitious mindgames as she and the class Sherlock try to catch each other out. If I'd cared about Nana, this might have been compelling.

This is the big one. Nana grows. To her astonishment, she finds herself stretching beyond her own self-definition. She gains a friend. She becomes an interesting character, because she's becoming human.

Towards the end, there's even an actual detective story. Everything until then had been a villainous inversion of them, since we know the killer's identity and we're watching her get away with it. Nana isn't necessarily the only killer here, though, and the last few episodes include a genuine mystery.

I particularly liked the ending. It's strong and satisfying.

This is based on a manga that's still running and there's clearly plenty of story to come. Even leaving aside the implications about Nana's mentor, there's a conversation to be had about Michiru's projected kill count. 150,000+. Where did that come from? Let's talk about the potential kill count of you, or me, or pencils, or modern medicine.

Would I watch a second season? Probably not, but it's possible. That would depend on whether Nana's character development continues, or gets reset for more assassinations. Would I recommend this show to people? Absolutely not. I'd expect most viewers to find it a dour, horrible exercise in I Don't Care About These People. Does Nana deserve our sympathy? Nope. There's no point after ep.1 when my idea of a happy ending wasn't Nana being tortured to death. This kind of material clearly has its fans, though, and it's true that the last few episodes took a strong upward trajectory.