A
Personally I'm having trouble getting into this series to be honest. I do enjoy laid-back isekai with harem elements and some action, so I should probably like this series as well, but... I just can't seem to get invested into any of the events and characters at all. I want to like Black Summoner, but I can't seem to feel anything but apathy towards it.
When I want to read fantasy or rather, isekai in particular, what I'm looking forward to the most is finding out about the world, it's races and societal structures, and how the main character survives and interacts with that world and the troubles that come along with it:
Does he/she try to innovate, trying to bring modern conveniences to a less-developed world? (Rimuru in Slime, Satou in Death March and Ash in Fushi no Kami)?
Does he/she try to settle in, but use the knowledge from another world to further his/her own goals? (Tanya in Youjo Senki, Myne in Bookworm, Yuto in Ragnarok and Veight in Der Werwolf)
Is he/she trying to bring cultural change to the world in some form or another? (Souma in Realist Hero)
Is he/she just trying to make the best of a new opportunity in a new life? (Van in Death Mage, Rudeus in Mushoku Tensei and Azusa in Slime 300)
Is he/she just simply doing his/her best to survive? (Luciel in Great Cleric)
Kelvin differs from most Isekai protagonists in the fact that he has lost his memories. I don't think this is a good setting to be honest, as it makes Kelvin a blank slate and leaves him without any powerful motivations. In a sense he is trying to make the best of his new life as well, but without any past, it feels completely different compared to protagonists like Vandalieu, Rudeus and even Azusa, who all have tragic pasts. I'd probably still be fine with it if Kelvin had some difficulties at least, but Kelvin and his companions are so ridiculously OP the biggest problems they seem to have is sleeping in late in the morning, which is a problem completely lacking any feeling of fantasy. It also doesn't feel justified that they're so OP, there's absolutely no way a skill like double skill points wouldn't be common knowledge in their world. And even with those growth skills, the speed of their growth feels silly as well.
Most of all though, Rion, who I thought I'd end up really liking. Even if I accept her ridiculous growth as well, I can't accept that she was, from the start, mentally fine going on a killing spree against those spies surrounding Kelvin's and the group's home - you'd either have to be a psychopath or experienced enough in killing to have become emotionally numb to the act to do that, even if it is to protect someone dear (she wasn't comfortable with it at least). I'm probably taking a light novel where the simplicity is supposed to be the charm way too seriously, but it is likely why I can't connect with any of the characters or events at all.