Going out on a limb after reading everything so far, I imagine Mc is either going to realize far too late how legitimately insane this elf woman he’s enslaved is and will not be capable of figuring out a way to “fix” her or whatever’s waiting for them in the southern continent is going to strain their relationship one way or another, given how generally capable the two are and how little potential there is for conflict between them there needs to be some a significant plot point introduced to prevent the story from devolving into “my life with my jealous slave dark elf wife”