Fuurou is the author, is this a female or male name?
@SonicWizard Slavery was an OVERT common practice for nearly all of human history. Only in what, the last 200 years has it been not acceptable in an overt fashion.
The era of these times, if you are not ignorant to all the other factors that lead to slaves (not just people stealing other people), it doesn't make sense to be so against it.
Most of the manga though, have slaves in it because they keep using this medieval fantasy setting. It is prevalent and nonchalant because it matches the setting. It honestly kind of ruins the story, when you have authors trying to act like it can be completely undone for modern day reasons.
While subtle slavery still exists, we will most likely end up seeing overt slavery again in the next 100 years, due to how history repeats and due to how our modern society is on the cusp of collapse.
Some modern people (especially women) may say, "I'd be damn if I had to become a slave to survive!", yet there are cases of "modern" people on the verge of starvation and seeing them offer up their life to serve someone just so they can eat, I can easily see it becoming a thing again if society collapsed.
We are supposedly due for a Carrington event in the next 20 years, and because of how perverse and degenerate the society has become, I would not be surprised to see again become part of human history.