Having watched a full playthrough of this shit now, I can say a little more about the game aside from its bugs. It has a good variety of shot types, the fourth stage goes really all-out in trying to resemble a corrupted video file, and some of the enemy layouts are kind of interesting, but it misses a lot of replay potential by keeping enemy encounters separate rather than letting them overlap if they're left alive. Thanks to this, there's likely a low-ish limit to the kinds of combos you can pull off, which gives you little reason to replay this for scoring once you've beaten it and seen its (pretty mediocre) ending.
Also, yes, the game's promotional material, log entries, cutscenes, and endings use random anime art off the internet. Yes, it is on Steam, Itch.io, and the PS4 store. And no, I doubt he got permission to use any of it. This plus the PS4 version crashing a bunch too doesn't bode well for Sony's quality control, even though the dev likely tried passing off the crashes as part of the glitch aesthetic or whatever.