Well, bestiality is wrong because of consent, so I guess it's fine? What about age, though? Isn't the monster still a child as far as the elf knows? Isn't this kind of like grooming a child to be a sexual partner? Power dynamics of a relation between a pet and its master are also questionable. Somehow, I've enjoyed it anyway. Then again, I've been recently reading "1 x 1/2", so maybe my concern for morality in manga has temporarily shut down. Either way, I need more of this.