This was a really hard movie to decide a score on.
To start, and most obviously, the animation. It's not great. I'd go so far as to say it's not very good. It's not Ex-Arm levels of bad, but that's a low bar. All of the characters feel floaty and weightless, which is especially obvious when Deemo picks the MC up. Furthermore, the environments are blended weirdly. The school walls are empty and bland. There's no texture and it looks like no one and nothing has thought of touching them. The texture on the plants are decent, and the visuals to pair with the music are fine. But nothing is stellar.
The actual music itself is pretty solid. There's a couple of pieces that made me go, "Woah that's not great midi," but it was still beautiful. The music definitely drove the movie and it did a good job of it. Furthermore, I think this is the best movie I've seen yet that depicts what it's like to play and listen to music. I would think to myself, "Hey, this piece makes me feel like I'm in this situation," and then the movie would transform into a similar idea. It was great. That's where the movie gets as high of a score from for me.
Other than that, the story was decent. It served the purpose it needed to. It was predictable, but that isn't a disservice to this movie, it just means everything was set up well. The climax itself does fall a little flat though. I think if I had played the game that goes with this movie, I would have enjoyed the story more in that medium.
Overall, I think people will enjoy this movie if they go to it specifically for the music. If you want to be wowed by a great story with beautiful visuals, go watch SpiderVerse or something. I would rather come here for the music though.
P. S. Definitely watch this subbed rather than dubbed. I watched the first 10 or so minutes dubbed and really needed to switch. Made the experience a lot better.