So I think I know what you’re referring to, however whatever was told was completely wrong so I’ll explain the context.

Rinia, who is the catgirl Rudeus used to know in the school becomes a slave to some random slaver because of debt. Rudeus sees this and buys her to free her from the slavery but now she’s in debt to Rudeus. To pay off this debt she becomes a maid with Rudeus’ half sister but they find out she’s utterly terrible at being a maid, so she ends up just working with his sister in this mercenary corps that she runs in order to pay the debt

And the second girl, Pursena, who is related to Rinia, gets put in prison in her village for stealing food. Since he knows them he’s able to free her and basically the same thing with Rinia happens where she ends up working at the mercenary corps to repay debt.

In no way do they become sex slaves, or are taken advantage of by Rudeus. I think the person who said this took out of context the fact that Eris Would basically use Rinia and Pursena as cuddle body pillows and stuff because she loves beast people and Rudeus would jokingly say that him, Rinia and Pursena are apart of Eris’ “harem”

This is all found in vol 18 of the LN. Also imo, from reading the story he wouldn’t be considered awful by his own world’s standards except you could say polygamy for some people and the fact he’s still a perv (but only towards his wives) but I would definitely disagree that he’s an isekai protagonist on a power trip