@robotcat
Do you know whether it's a harem in the first place?
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By the way, I disagree with Mangareader. The tsundere aside, I believe that a shapeshifting and potentially cannibalistic demoness is a way better love interest than a useless, so-called city-toppling beauty whose only purpose is to draw the attention of lecherous young masters and add nothing to the plot aside from dragging the protagonist down and being baby-fed cultivation resources and hard-carried so they can still somewhat keep up with the protagonist (which they would have never been able to do on their own) and remain relevant enough to, again, attract the attention of young masters and serve their purpose as brainless plot devices. On top of that, that demoness seems to have more personality than the doormat-like love interests that infest cultivation novels.
So I'd say both the protagonist and us, the readers, would actually be very luck indeed if she becomes a love interest.