I beat the boss!
I like action games in general and I like your take on combat system where you need to balance your moves based on two resources that enemies have. I also like the fact that you used youmu's twin blade settings. It's often getting ignored in other fangames and I'm very glad to see it here.
However controls and combos are a bit cluncky that I don't really understand how it works. Sometimes I can do a cool combo but sometimes it just slashes once, and boss hitbox seems to be much larger on the bottom side while almost non-existent on the upper side, which was kind of deceiving but it's very easy to kite after I get used to it. Potions and apples in the grass also helped a lot.
Some tips for the boss: it's easier to hit it from bottom after it attacked, and if you have problems with controls I recommend hitting it once or twice per boss attack. It moves very slowly and you can get heals from cutting grasses safely so it's fairly forgiving. Get it around 5 hp and 5 mp then you can just go ahead tanking the hit and finish it with AZ combo.
Although story is underwhelming and it doesn't really ring me a bell about folklore, legends and such, gameplay and design are excellent by themselves.