Why not just have good guy corpses around too? My concern is that they thought the only way to make it about a girl is by having a reason to not have guys(which is unnecessary) and that's sort of what happend. But is it a bad reason within the story, nope, it isn't. It works just fine. I can also understand that the manga-ka wanted to jump into the action and have the character already be seasoned as oppose to freaking out. That means the explanation has to wait until another character is introduced into the world. I would have preferred this earlier, maybe with a different Shikabane than the main, in that way it wouldn't get in the way of her characterization. But it's fine.
We're given no indication as to why a living thinking girl is considered not a girl just cause of the corpse thing, it's just silly. Even if it's a dead thing in the fiction, it is still thinking and maintaining the personality it had, there's no indication of a change. Though It might be how the witch hunters in witch hunter robin were thought to be able to freak out and turn evil, despite that they were treated alright until later on in the story.
It kinda reminds me of Gun slinger girl where it sort of makes a girl tied to some guy even if its just for work and without the evil brain washing in that other series. It's also just needless. You don't need to make the situation unique just cause its a guy and girl, that doesn't have to be explained. But I don't think there's any fetishizing going on though, and it is more of a work partnership. And if it's just coincidence then that's fine, if it isn't, I hope the manga just points it out that the sect is reluctant to have women as monks for whatever reason(maybe cause it's combat oriented). This could also be tied to the father-daughter explanation that's behind the ritual, and that'd be fine too.
Some of the monsters have interesting visuals. The interaction with the slayer and her priest can be nice. And despite the corpse's healing abilities, they aren't very super powered, so the danger of loss(and death) is there. Aside from some moments of bad dialogue, the plot itself can be good.
I do like the characters, and the story overall reads closer to a seinen story. It can be action packed but it spends time building up what's going on, and the main character does look cool double wielding Uzis.