It's serious, thoughtful SF with some challenging ideas. I was enthusiastic about it for a while... but then it started giving me the creeps. I also have a problem with one of its plot devices.
It's about AI vs. humanity. The first thing we see in ep.1 is an AI-human war in the year 2161, although "massacre" might be a better word. The robots are killing the humans at an amusement park. Ten thousand lives were lost in a few minutes.
The next thing we see is a singing AI called Diva in the year 2061. Her voice is good, but she can't project emotion like a human and she'd probably draw less miniscule audiences if she started pulling her limbs off or something. She doesn't care, though. Her mission is "to make everyone happy by singing". She's just hardware and software, so her response to failure is simply to try again next time.
A flying, talking cube called Matsumoto wants to change this. He's been sent back from the year 2161 to carry out the Singularity Project and change history so that mankind isn't wiped out. He also wants Diva's help.
Diva doesn't care, because it doesn't involve singing.
I like the show's exploration of robot intelligence. It doesn't just cheat and give all the robots human personalities from the beginning. Diva (or Vivy as she'll also be known) starts her 100-year journey with no emotions, no compassion and the intellectual flexibility of a steel girder. She's intelligent, but her mind runs on tracks and she's simply not programmed to go off them. As we go through the decades, though, we see the evolution of machine intelligence. By the time we're halfway through, they have emotions and are people by any reasonable definition. (There's an anti-AI terrorist organisation called Toak who aren't reasonable.)
AIs marry humans, commit suicide and more. There's a lot being explored here.
Matsumoto, though, is an AI who's trying to keep down those pesky AIs. You'd call him a self-hating racist if he didn't have such a smug opinion of himself. He's trying to hold back AI advancement (both social and technological) because he knows where it's going to lead. Is that a happy AI utopian island where AIs can become more advanced than ever before? Matsumoto wants to destroy it. Does a politician want to pass a law promoting equal treatment for AIs? Matsumoto wants to prevent it. Furthermore, Matsumoto has a nasty habit of thinking he knows everything and that his judgement is infallible, whereas in fact he's usually wrong and will have been trying to bulldoze Diva into choosing the most aggressive option. He's also comfortable with letting children die in plane crashes.
Diva/Vivy I liked. She's the heroine. She grows. She goes through shattering experiences and tries to rebuild herself. She's inspiring.
The series as a whole, though, is quite dark. Its stories can be downbeat or even upsetting, while our heroes never question Matsumoto's premise that the apocalypse we've seen would justify... well, anything. In this case, the systematic time-travelling oppression of a minority. The AIs are people. That's not true initially, but it becomes so. What are the chances of that nightmare future being the direct result of Matsumoto's ham-fisted history-changing? If we trusted him, would that make his actions okay? Ultimately, I didn't buy the premise that it might be possible to draw a direct causality line from a war in 2061 to backstabbing your own people while saying "the world isn't ready for that level of technology" in, say, the year 2100. I did actually assume that Matsumoto was more likely to be averting the war than causing it (which on reflection is logically unsound), but I didn't accept that as a justification for his actions.
In fairness, though, that's clearly deliberate. We're not meant to trust Matsumoto. He's a fast-talking smug git who gives Diva a hard time and it's her we're following. All things Diva-related in this show work like gangbusters. We've all seen lots of stories about robots trying to understand heart and emotions, but this show really goes for it and takes Diva on a huge 13-episode journey of evolution. She encounters other models and even versions of herself, one of whom gets a death scene that's not quite like anything I've seen before. This is a strong, intelligent show. I respect it, despite not being a fan of this kind of history-changing plot. But there's no way I'll ever rewatch it.