People always bring up Usagi Drop in situations like this, but its memetic qualities have spread so far that I feel like it's rare for people to even know what the whole drama with Usagi Drop actually was. I'm sure you didn't mean much by mentioning it but I think Usagi Drop really belongs in its own category of manga like Gal Cleaning which pissed off all the readers with its own drastic tonal shift. Bringing UD up whenever incest is mentioned kinda dilutes what made it such a big deal in the first place.
There's room in the heightened escapist fantasy space of fictional manga for non-blood-related incest plots, where all questions of problematic power dynamics and grooming and age gaps are brushed aside with the assurance that it was destined to happen and the parental figure has no ill intent and it's a true authentic love or whatever the fuck the justifications may be. There's even room for actual blood-related incest with actual malicious grooming. Most readers will find that disgusting, and rightfully so, but people can write whatever fiction they want and the onus is on the reader to choose what they consume and stop reading things that they obviously aren't going to like.
What made Usagi Drop so upsetting to so many was that it spent the entire first half of the story being purely about Daikichi learning to be a dad, almost no hints that it could be going in any other direction, with Rin's romantic feelings being extremely subtle if they even existed at all. Most readers were already committed to what they saw as a pure story about family by the halfway point where suddenly everything shifts and it's about a high school girl crushing on her father figure. And then, out of nowhere, comes what feels like the asspull of them not being blood related. Surprise!
Even then, people who were familiar with josei manga tropes saw it coming from miles away, another part of why Usagi Drop had so much impact was because it reached far beyond its intended demographic. Plus, despite the not-blood-related asspull, Daikichi was never her dad in the first place, he was taking care of who he thought was his grandpa's kid, so they thought they were blood related but he was never her actual father. He thought he was raising his half-aunt who was a fifth his age!
But I'm getting off track, point is, UD went down in history for basically jumpscaring people with incest after they'd already been reading for 44 chapters, and then not even having the balls to commit to it being incest with a contrived twist.
This manga has been extremely clear from the start that the dynamic is going to be Klael seeing Reina as a static protagonist that he's just pushing down some kind of story path, while Reina sees Klael as her future husband. He's not even really a father figure, he's a priest taking care of an orphan. Nobody has any right to complain that they didn't see it coming if the story goes down the daughterwife road. If seeing "daughterwife" just now gave you a feeling of deep disgust, that's a good thing, but you should probably just unfollow the manga now and forget about it.
Having read the WN... yeah, sorry, if you aren't open to daughterwife endings you're in for a bad time. I feel like this barely qualifies as a spoiler since the manga is already so blatant about how strong Reina's feelings are and it's obviously going to keep playing out this dynamic rather than have it be "just a phase," but if you have any hope that this might be a pure platonic familial love just throw that hope away now. Like c'mon man the manga has the romance + loli tags and everything.
