Haha, "slaves are historically accurate....for a fictional society where magic exists" is some big brain creepy slave apologist bullshit. The problem isn't that slavery exists in a fictional world (I mean its *a* problem) it's the fact that the main character, who in isekai is generally a person from modern day Japan, instantly buys (literally) into the slavery system. Slavery should be abhorrent to anyone from the modern world but they generally always leap right into it, often compounding it with sexual slavery. It's even fucking stupider here considering the stories central premise is the main character wants revenge because...HE WAS TREATED LIKE A SLAVE.
I suppose I should go and as suggested read one of those "stories for children" that doesn't decide to cast away its core plot structure to pander to creepy fetishes. Oh shit did I just deny the fictional history of an imaginary magical world? How surreal of me, I hope I haven't strayed into the danger the poster below mentioned. Next thing you know I'll probably deny that magic and dragons exist.