The art for this is thoroughly mediocre and there are quite a few really awkward looking faces. It's got its work cut out for it to keep me interested.
Japan has weird ideas about slavery. Largely, I think, because they don't have the lengthy and more recent history of chattel slavery (the slavery most people think of when they hear the word.) that the west does. Most manga or LNs with slavery elements seem to be more patterned on the idea of indentured servitude or "non-free labor" where people are contracted into the service of others as penance for crime or debt or because they have no other option, being subject to the servitude is either a choice by the person or is accepted consequence for something they've done, and there are certain base expectations of care on the part of the "owner". It also doesn't help that Japan largely tries to downlplay or distance any association it has with slavery or slavery-like situations in recent eras, such as broadly trying to pretend that they didn't use "comfort women" or POWs as de facto slave labor during World War II.