We never learned what the sacrifice was for, right?
I want to say him not being sacrificed yet is the reason, but the maid said "there is nothing you can do" which kinda implies it's not that. Unless she chose not to sacrifice him in the end.
It's good to see the story finally start to go somewhere, tragic as it may be. Though I'm pretty sure the author's setting it up so that he's somehow the key to curing her illness.
@Nakanowatari The novel it's more or less based on is only 44 chapters long itself. The manga was never going to be hundreds of chapters long. Not everything that's short got axed.