Thanks for an important societal history of slavery that I did not know, too.
Two things to read if you haven't. One is the Travels of Marco Polo c.1300AD-- it included the Korean peninsula, if you did not know. Here is a good English translation from 1958 (he notes who has slaves and who rules who, and how).
https://www.amazon.com/The-Travels-of-Marco-Polo-audiobook/dp/B00009OYYK/
The second is I wrote about the fact that slavery is still fundamental today and really has not gone away, at all. Which you kind of say too.
A lot of current talk about slavery I think misses the mark on what needs discussion and concern. The recent Korean history you are giving is worth understanding by a wide audience. Back in the 1600's the Philosophers of the Renaissance in pursuit of Truth called these "social contracts."
