I think it’s an anime about vampire. If i remember correctly the first episode/chapter was a scene where the main/male protagonist was watching a building full of vampires or demons with his team. One of the guy he was with had a cover as a musician but turns out he had a gun in the violin case.... can’t remember much but the ml rushed to the building and the others had to follow on him. I think ml had a gun or sword. That’s all i remember hope somebody can help.
I had never watched it at all, but is it Hellsing? Somehow that's what comes to my mind when you mentioned vampire