The series has some major plot holes, but I was/am still willing to forgive it and shut my brain off just a bit. They are actually exploring a mechanic where the protagonist has no offensive abilities of his own, and has already become a pariah so his last resort is buying a slave. So that, at least, is something new. Its rare to see fiction in any medium where the protagonist isn't just an anti-hero, but actually acts like a villain. But not moustache twirling over the top evil for evil's sake like Overlord.

(It's obvious he won't be one forever, but it'll be nice while it lasts.)

That and the animation is actually pretty well done.