It just feels icky. The way half Beasts are treated (mostly) is rather disgusting, slaves, sex toys or pets, all of it is just not it. Treating such humanoid looking people as so much less, it's just gross. And calling sex with them "beastiality" also is weird since they are mostly just like humans, except like one or two small details. Haku likely is meant to be an adult, of sorts at least, but with how innocent, naïve and clueless, it just makes him feel way too child-like. Considering that Haku doesn't understand what is going on, it's some form of dubious consent, though Eiichi is trying his best to limit it to necessary and not be a damned pervert for once in such an AU (Except for one time, I guess). Some unnesseary drama with that woman that wants to marry Eiichi, and manipulates Haku into running away to sell himself, which was rather easy since he is just that naïve and clueless. What's also weird is how heats are treated in this story, as if he can just go into them as he pleases, every day, whenever he's touched and horny... That's just not how heats work and it makes it rather cringe to read. The only thing good about this story is that it is a pretty art style and that the Seme is not a rapist pervert.
Kemono wa Okumade Aisaretai