Great concept! I am a big fan of Okami and its drawing mechanic, and believe there is something there to keep exploring, so I am always in for games that play with that, like the spells in this one!
If I had to give feedback, it would be to add enemy variety that interacted better with the main mechanic, like one getting invulnerable if you drew a loop with another extra enemy on it, or one that messed with your loops to introduce some kind of enemy priority to the player.
I really liked the idea of the crystals on the sides to give positioning control to the player, which is often important in shmups. Also, I liked the resolution at the end haha. Good work!