This was an interesting premise and a good start to your AU. I am very interested in seeing how you flesh out the characters and how you build conflict with the werewolves and vampires.

One bit of constructive criticism would be to proofread and spellcheck a little more. Just some small grammatical and spelling errors here and there. I would recommend a beta reader or having someone you trust read it and tell you any mistakes they catch.

One last thing. Something that I think would be awesome is if Asta and Yuno were like half demon and half angel. Vampires and werewolves exist in your AU. Can demons and angels exist too? I think it would be awesome if the vampire girls fall in love with a half demon spawn, who unknowingly wields dark powers that even vampires and werewolves are afraid of. And he's got a half angel for a best friend/brother who wields heavenly powers and can fight alongside him.
Just a recommendation of a little idea that I had. Hopefully it inspires you. Great first chapter. Hope to see more