Edit 2025:
I must say, despite the later graphic sex scenes that bother me due to me trying to quit pornography, and it's slow plot progression, and the occasional lack of common sense the non-plot elements of the story suffer through... the good parts of the story seem to outweigh the bad parts significantly.
The story starts out simple, with an isekai of the main character dying on his way home to his little sister (who now has no family left). He gets some cheats and then ends up in a starter town. From there, he gets a cute wolf girl slave as a temporary dungeon guide and decides he needs to buy her before some noble buys her. And much later on we learn why she was a slave, and while it's technically not fair, it makes complete sense.
And interestingly, while the noble in question is a bit dumb and shortsighted, he turns out to be an okay guy who is humble enough to learn from his mistakes and do better.
Yes, this manga is a harem manga, for both the main character and other characters who have their own harems. Yes, some of those girls in the main character's harem are slaves. But not all of them, and each is given their own backstory as to how they ended up joining the main character (and those tie into the plot or mysteries surrounding the plot), whether that's as a slave or not. There's a genuinely high amount of effort put into the characters on all sides of the story.
Honestly, you would be excused for thinking this manga is just an average isekai for quite a long time. But slowly—and I do mean slowly—things start to come together in unexpected ways as it turns into a massive adventure story with lots of towns, countries and contained subplots in between the larger plot and its subplots. There are several major factions at play, and most of those factions are not completely unified, either.
If you can endure the earlier scuff, this story really begins to reward you in ways you just don't find very often. Give it time; there's a surprising depth if you've got the patience.