It's the movie sequel to Rascal Does Not Dream of Bunny Girl Senpai, which I'd liked a lot. This film... well, I'm less sure. It's emotionally powerful, it'll surprise you and it explains the big mystery that had been hanging over Sakuta since the beginning.
Downside: it basically skips the ending. It's been building up to a spectacular final act that takes the show's Rules of Weird Stuff to the next level... but then doesn't show any of it to you. We jump straight to the consequences. It happened while we weren't looking. Stuff's been fixed, but we have absolutely no idea about what happened to get us there. Admittedly we do learn what happens to everyone, where the relationships are and why it's left our heroes in a good place, but dramatically it's like having your pocket picked.
That aside, though, it's a satisfying film. There's room for everyone, even relatively overlooked characters like Koga. The Sakuta-Mai relationship is, of course, at the heart of the film, although here it's become an involuntary triangle. Makinohara Shouko appears to have solidified in our reality. In two bodies.
There's a girl who needs a heart donor. There are consequences to this. There are some imaginative rules about how the universe works in this reality. It's well thought out, but also sufficiently left-field that you'd probably need to spend fifteen minutes drawing a little chart to satisfy yourself that everything here tied up. Sakuta's nicer to talk to these days, incidentally. (The series gave him character growth, like everyone else.)
To be honest, I don't have a lot to say about this film. It's the kind of intelligent, essentially simple and tightly woven SF story that doesn't need picking apart and you couldn't do so anyway without getting into spoilers. I don't have any nitpicks. I like all the characters and the plot holds water. It hasn't left any loose threads to pick at. It's absolutely solid... except for that ending. I'd probably need to rewatch the film to decide what I think about that. Right now, it's my least favourite bit of this franchise, but one day that might well get revised upwards.