I did manage to clear the game, once I got through stage 1 and 2 which took a few tries, I was able to beat the rest on my first run (somehow). Though I'm pretty experienced with platformers, and probably got lucky against Suika lol
Pretty ambitious all things considered. I was surprised by how long this is.
I basically agree with what's been said so far regarding the difficulty. With checkpoints and/or maybe health pickups in the stages themselves, I think the difficulty would've been really good, but as it stands it's very punishing. I also want to echo the issue with the particle effects from Remilia's bullets blocking enemy projectiles when they're first fired. This made some bits more difficult than they should've been.
Something I noticed was that when Remilia lands, there's a slight bit of landing lag and her horizontal momentum comes to a complete halt. I found this broke up the flow of movement, though I did consider that maybe this was to make landing and staying on the small platforms you create easier? I can see players sliding/walking off after landing being a potential issue. If that's the case, I can understand, though there probably would be a better way to go about this than universally giving her lag upon landing. For example, something the game already does is have the stand-able collision of the platform extend beyond the visual.
Something small but really stood out to me and made me laugh was the sound effects for Remilia's flying and her crouch. Was just very goofy in a kind of way that suits her, since her whole shtick is being the spooky scary powerful "Scarlet Devil" while then also acting like a spoiled child. Also her sprites are just adorable~