The world needs more Seiga with a shotgun. That art is great. Glad we're getting more Seiga games.
As for the game itself:
The explosion indicators needed to have better contrast with the background, especially since you can expect the player to be looking further up the screen where enemies spawn. The enemies that die to the right of the screen drop items you cannot pick up.
Suika's first attack was pretty fun. It felt like a bullet hell at that point.