Hahaha, I laugh at everyone who complains about the rape.
You don't have to go anywhere to a fantasy world to have rape hell, it's everywhere around the world, especially in non-European countries, where the strong just take whatever they want, be it money, goods or women, by force.
And about the naivete of the female characters: Japan is +- the country with the least number of rapes happening all around the world.
And while it's all around in their pop-culture, do you think they even believe that it would be happening to them in reality?
They are so much protected by their own kindness and self-focus that they lost touch with reality.
Europeans aren't better, either. Poisoned by Socialist-Liberalist ideology, how many European women have gone off to African and West Asian countries just to get raped and/or killed, because they were taught that every people on earth were as kind and empathic as their own?
Rape was and still is part of military strategy in Muslim countries, also mainly because Islam ideology allows it and makes it a virtue to rape the Kafir women as they are spoils of Jihad. They can even rape their own wives and yet most people in the world don't care/ give af.
So those who think this kind of rape is gruesome or whatever need a reality check.
Yes, the author pulls the rape card a lot, but it's way more realistic than your peaceful isekai bullshit story where evil people are limited to slave traders and/or thieves.
Human evil is everywhere and way more brutal than what is shown here, it's just that the author uses non-human adversaries to present human evil to the audience, which is probably 100 times more acceptable for the Japanese audience than the human evil route in e.g. "Kaifuku-jutsushi no yarinaoshi".