I might struggle to get to the 2200 character minimum for this review. You can only say so much about these types of shows and almost everything you can say has been said already. I have seen way to many of this exact type of show. This is where I have to concede that these kinds of shows are my guilty pleasure. A common thing for this genre and this type of show in general is that its very easy to watch.

Having seen dozens of them, let me start out by giving a basic layout of every single one goes. - Average dude (ages vary from 16-20) gets isekai'd into a generic fantasy world. - Is given or gets a very special power (Usually says it in the title of the show). - Joins a guild in a pleasant town. Goes on adventures, gaining girls along the way. - Faces moderate threats early on, but quickly becomes so OP that any stakes are gone.

Almost all of these anime are adapted from Light Novels. They all also have one or two gimmicks. The first is always the power they have, in this case its summoning. If there is another gimmick its usually to do with the world. Whether it be a quirky magic system or extra mechanic and in the case of this show its the found family aspect of the cast. The main character is either an anti hero or paragon with very little deviation. Because of this, I lable isekai where the MC is a monster or the "villain" as different enough to not be included. That idea isn't as overused and still is being explored.

First off, this show isn't bad, but its closer to medicore than good which is probably the worst thing an anime can be. This show like the dozens before it will be forgetten about by the end of the season. This show is not worth being remembered. It will make a great one day binge watch for someone craving a power fantasy anime and not much else.

My score for this show is gonna be a 55. As I said in the previous paragraph, its very close to painfully mediocre. 50 is average on my scale.

I was talking to friends while watching this show and said to them, "I hope this show isn't pro slavery, I hate when isekais do that." A week passes and I am watching the new episode and halfway through I say to myself, "Damn... another pro slavery isekai."
Black Summoner has decent characters, a kinda interesting world, and the plot is engaging enough to not lose you. This show has potential as most of these kinds of shows do, but it moves on from world building or character moments way to fast for anything to truly matter. Yes, you've established the major kingdoms, but have not given us a reason to care about any of them. 12 episodes gives roughly 4 hours worth of time to tell a story, but I don't blame the production team or studio. Light Novels are written so that you get to the big action scene or harem scene as quickly as possible. Threats are established then the MC comes into conflict with them.
Its so hard to talk about Black Summmoner alone as its own thing, because its not trying to be its own thing. One of the worst things about the show is that slavery, yes the buying, selling, and forced labor of humans/humanoids, is treated as fine.

Spoiler, click to view

This creates an insance conflict of themes and morals when the MC buys a slave and thanks the slave seller, but then stops a gang of bad guys who were doing the slave trade. The MC fights slavers with the help of his own slave.

But even this isn't unique to the show, 1 out of every 5 of these trashy isekais will have this exact same attitude towards slavery. It makes the show worse, because this show is generally very light hearted so when the tone doesn't shift for slavery its a whiplash to the viewer. I don't care that in japan they aren't taught about slavery and so its much less of a cultural taboo, it doesn't change how universally wrong slavery is. You can have dark and taboo things in media and do it well, this show is does not do it well. Black Summoner is a trashy generic power fantasy isekai with some neat ideas and a generally likeable main cast. Its a great popcorn anime to binge when you are bored. It has almost no merit outside of this however and there are dozens of isekai with similar set ups and premises that do a lot more.