Saskuati

The plot is the most generic thing i've ever seen and the characters are just like potatoes, they don't have any development and if any of them die it doesn't impact on the story because no one can relate to them.(at least me and my friends can't, but this is just me, so go read the manga to have your opinion)

The protagonist just got his powers being summoned a bunch of times and guess what? He is now a vampire with some black clothes and hides his power, why though? This is the only thing i didn't understand, why does he have to hide his strength? (I really just wanted to know, is he gonna be hunted down for being a monster?) 

The characters are the same you see in every isekai manga, they don't question the person who summoned them and didn't even try to see the whole situation before accepting fight to death with other living beings, but again, this is the generic manga that most mangakas use to get better at drawing and to get some income.

The art is not bad, actually i quite liked the way the mangaka did the characters and the background, it just needs more details.

Again, this is my opinion, so go read the manga first (if you want) and then you can say if you like it or not, you are free to criticize my opinion and I encourage that, the only thing I don't recommend is reading my review of the manga and not seeing it because you think it's not worth it.