If not for the game having the obvious doujin graphics and audio, one might swear this game was made by CAVE employees or former employees thereof. Imagine the scoring mechanics of Ketsui but with the isometric horizontal perspective of Progear or Akai Katana. Solid game if you want something relatively conventional, it doesn't do much to stray from the usual arcade bullet hell tropes.

Also yes, the game is not on Steam. It has only been sold as a Japan-only physical and as a DLsite digital. If you have a little time to set up an account there, the game does not have any DRM to worry about nor do you need to install some launcher app (just run the game straight from the executable), so it's absolutely worth the extra legwork.