It is a good anime, from the production quality, to most characters, to plot, to combat.
The sense of progression in this isekai is among the best. It does not beat around the bush.
I don't even understand how the fuck people here are so fixated on the slave part. He couldn't find anyone for his party, he didn't have any attack skills prior, so he had to buy one... How is this such an offputting concept I don't get it.