It's a cute show about a cat (Haru). The twist, though, is that her owner (Subaru) is a professional author with some kind of disorder who hates being with other people, struggles even to go outdoors and has no living relatives. His parents died in a road accident.
They're both idiots, obviously, but in complementary ways. Haru used to be a stray. She was the biggest of five siblings, but they're all gone now. She only has a cat's understanding of the world and will regularly misunderstand the humans around her. She is, though, intelligent enough to realise that Subaru's a disaster area who needs to be reminded to eat. (Seeing him collapse from hunger is a clue.)
In other words, the show's cute without being a bland marshmallow. It's lovable, but underneath is grief, dysfunction and death. That's a good thing, obviously.
The show has two modes. A typical episode will be two-thirds Subaru, in which he's the protagonist and Haru can only make cat noises. After that, it'll switch to Haru Mode, in which she has a voice actress and we see earlier events replayed from her point of view. This is a lot of fun. You could sail an ocean tanker through the gap between Subaru's and Haru's idea of what's going on. For starters, each thinks they're the other's minder. Haru regards her human as a hopeless case who wouldn't be capable of anything if she wasn't guarding him.
Subaru improves hugely. By ep.12, he's learned how to interact with people. Animals drag you out of your bubble, e.g. at the pet shop or the vet. You find yourself talking to other pet owners. Besides, Subaru has two people who keep showing up at his house, whether he likes it or not. One's his loud childhood friend, Hiroto, who's not bothered by anything and will cheerfully invite himself around to shove food in Subaru's empty fridge or bring children to see Haru. The other's Subaru's editor, who loves cats and understands that his client is hard work.
The show's about (mis) communication, I think. It's built around the Subaru-Haru gulf, but there are other examples. Subaru's job is all about words, but he can't use them in person (e.g. to tell people he's an author) and so he creates misunderstandings. People worry about whether they did the wrong thing, whereas of course it wasn't them at all. There's also a slow-burning arc about Subaru discovering how much he hadn't realised about his late parents. (If my son were like Subaru, I'd worry about him too.)
How much does the show fudge with its anthropomorphisation? How Disneyfied is it? Is Haru cat-like? Answer: it's pretty good. Her body language is spot on and it's a delight to see her walk, curl up, etc. Her thoughts usually feel like a plausible approximation of what you'd expect a cat to be thinking. I enjoyed it... but I see two cheats. Firstly, Haru's eyes are human. (The show tries to hide this by making them red, but she doesn't even have vertical cat pupils.) I can forgive that, though, because it allows funnier facial expressions. (Haru's liable to be enormously pleased with herself, for instance.) As for the other cheat, that involves Haru's dead siblings. As we see in flashbacks, they're helpless tragedy engines who can't do anything for themselves and are entirely dependent on Haru. No, sorry. That's not how cats develop. If one kitten can run and hunt, then so can its siblings.
I don't mind that, though. It's a nice show. Sometimes it's funny. Sometimes you'll cringe a bit at Subaru, but he's learning, with Haru's help.