Just played your demo! The art style is good, I like the 2 main character designs. The bullet hell is solid, and the switching mechanic is a good idea!
It did seem a little easy on my first play through (more on that later). I also didn't realize how narrow the "play-area" was at first. The forest edges could use a little extra definition to show that they are walls essentially.
I did go back and play again to see what would happen if you lost (that gameover screen!!) , and I found what seemed to be a bug. When the character is defeated, they still get hit by bullets and can insta-die before even reappearing. If there's a lot of attacks on screen, this means one hit can be game over. I'd suggestion resetting the players position, and maybe a very brief invincibility period when you respawn.
Nice work!