See, that's the confusing part to me. It's easier to directly splice the genes relevant to just reproduction than to splice all the genes that would make them look like an animal. And these girls don't look like test tube babies, so they must have the tech to rapidly mutate people too. And JUST the girls. All the dudes get to stay human for some reasons.
Even up to this point, I could roll with it if the premise wasn't "I swear, it's for the survival of the human race."
Like fuck dude, I would have even taken "asshole mad scientist released mutagen to mass Japanese population and the lack of clear human rights mean people can do whatever they want to human-animal hybrids." or "mysterious disease going around transforming people seemingly overnight." If you're going to go full degen, don't try to make it sound like that's the rational conclusion. There's no rational part about this plan.