The visuals, music and presentation are top-notch.
How much of this did you do yourself? It's very impressive.
I had some frustration learning this since the instructions are in Japanese, however with more time I began to pick up on more things. Over more attempts, I eventually went from not being able to defeat the invisible ship to making it to the end-of-stage boss fight. Some aspects of the mechanics (when it comes to the purpose of leveling things, etc.) I still don't understand.
I dislike the initial enemies spawning right behind you (especially since you're placed near the bottom of the screen), and I don't understand why you chose to have lightning randomly strike/zap the player. There's no telegraphing whatsoever for the lightning. Those two things feel quite cheap and should be adjusted.
Currently I can't figure out how to beat the end-of-stage boss. I've done some damage to it without even realizing what I was hitting and then I end up dying before I can figure out what's going on. I'm not giving up though, eventually I'll beat your build haha.
Last year I submitted Coma State Eden to the Game Development Challenge. Like your entry, mine is also very inspired by retro arcade shooters. Yours reminds me of games like Mars Matrix.