One thing I very much enjoy about this work is that this is not an isekai. Don't get me wrong, I don't hate the genre, but this one has a different, more emotionally honest dynamic to it.
Because the little girl has never been someone else, I feel that her strength and determination is truly her own, and not because she has the protective shell of another identity to rely on. When she is welcomed with familial warmth and luxurious care by the Salvatores, she isn't a tourist partaking in the exotic delicacies of a different land, a different life -- she only knows what she knows. When she declares in her heart that she will destroy the Sperado House and avenge all the sacrifices, it's much more convincing because she's not taking on an outside quest, this is really for her, or as she and the shadows would call it, for "us."