I really wish manga would stop using slavery as some form of drama piece, they either make it highly cynical to the point of comic villainy, or make it idealistic to the point of better a slave than free, both of which aren't accurate to how something like that would really work historically, for good or bad, it essentially becomes a 1 dimensional justification for "dis guy evil, dis person luv me for saving them" or "slave of choice" tropes.