Catharsis Factor: The slave trader is one of the most despicable characters Naofumi comes across, and many readers dislike how the source material tries to make him likable despite being a literal slave trader. Thus, it's safe to say that the only tears readers will shed when Filo bashes his skull in on Chapter 21 are tears of joy.
Friendly Fandoms: The fic has been received fairly well by the fandom of His Soul is Marching On to Another World (and vice versa), another anti-slavery isekai fic which stars famous abolitionist John Brown leading a rebellion against a corrupt monarchy to free the kingdom's slaves.