I understand this is your first game and seems to have largely been done on your own, so I'd like to start up front by saying it's awesome you did this in just three days. It's an ambitious idea and the fact you got it off the ground is an accomplishment in itself.
I'll start with the positives. The twin stick controls and the firing with triggers was very natural, and felt good on the controller. If there's one thing the game does well, it's definitely that. It also felt like a fair challenge, all told. In terms of gameplay, you got the basics down and that's the most important thing.
All said, there's a lot which can be improved upon too. Mima moves like a boat (at least on controller) for a game which seems to want to play hard and quick, which creates some issues. I accidentally moved my mouse at some point and the game spun around like I was on a merry-go-round and it made me sick, which indicated to me it was probably made for a PC experience. (Which is fine, honestly! Just different.) I also didn't really know what a lot of the different bullets did as there was no tutorial or indication. All I could do was interact and shoot. I felt pretty lost as a result, especially when I started carrying multiple types. And then the sound effects. Oh dear, the sound effects. That was extremely unpleasant, even with the volume down. Having some music to at least cover up 70 percent of that would have made it feel a bit better. I had to stop after awhile because it felt like the bullets were directly hitting my brain.
Overall, you aimed to make a twin-shooter game and it totally works. The premise for the scenario is pretty funny as well. The way you write Mima as haughty really quite works. The fact there's multiple endings is also very good as it encourages more play. The main issues are just some polish things, mostly with audio, minor navigability things and the UI (it was very difficult to read due to the fast action.)
Good job, and I hope to see you again soon!