This is a Touhou fangame.
It's a 2D exploration danmaku action game (AKA a danmaku Metroidvania).

You'll control Hata no Kokoro on a journey to find her masks.
Rather than clearing individual stages, you'll explore and find various items to power up along the way.
Four difficulties are provided, so you can have a good time if you're not skilled at danmaku action games.