Outright amazing. It didn't even have to be an "adult" adult game, the story is intriguing and written well enough to sustain interest. If I wasn't working on a minimum wage and living in a shit country, I'd pledge my wallet to this.
"How should magic work in my story?" is a question that can lead to sheer shithousery, if answered without respect to the concept. Your approach is convincing and interesting enough, which is saying something because many professional writers absolutely shat their pants trying to do it.
I hope you get, like, a couple thousand patrons soon. Because I need to see Siegmund wreck shit with that sword.