Like, I haven't seen anyone with even a bit of common sense in the novel, except the female lead here, and from what I remember, her common sense is becoming kinda dull because of the unreasonable things that keep happening around them...
Oh! And those who clicked here expecting a spoiler: That guy "dominator" or something will die very stupidly as expected from instant death. After that, one girl of his harem meets that sage from some chapter ago, that one who just threw the "hero" away like trash, yep, that Lain. You see, I think that she kinda wanted to see the extent of MC's power and sent killing intent(edit: nope, she didn't send it), which she discovered to be the trigger, to which the MC answered with his instant death(Edit: yep, from here on I remembered right, more details on the edit), at the first seconds she thought she was fine, but then she discovered that the instant death went for her true body and not the dummy she was using, so she died ^-^
Oh! And she made one "self" that was entirely different and disconnected and said: Meh, seems like I died, live however you want. And the girl who just suffered from information overload was like: Okay then, I'm going to find whoever killed the me from before and then chose how to live.
Oh, by the way, there's an arc where an asshole just turns a whole city into undeads, 'cuz he felt like, after all, why not let the whole city suffer for something that they haven't done and let them taste my great power? This guy of course died. I think Lain was still alive here and she just threw some things at the city because she was probing the MC to see if he can track her if she doesn't show killing intent. Seriously, isn't she way too curious?
(Edit: Yeah, not really wrong, just disorganized, at the same time that an apocalypse was happening in the city, Lain found one of the girl of the harem and decided to keep her and together with the girl, she just tried out to see if she was right: “Well then, how about if I don’t directly aim for Yogiri Takatou?” (Lain); the Harem girl was like: Maaaasteeer, better not do that... Heeey, don't do that, dat boy is just too unreasonable!
And Lain: Naaah~ I think I'll be fine, look, how about a clone? Lain B, go above that city and destroy everything.
But since MC is MC he killed Lain B and tracked her main body. Lain was disappointed at first, but then she discovered she couldn't move and then she realized he real form died.
"That was too irrational, it was an ability with strength to the point of it being stupid.
But, that was quintessential point.
That quintessential point was sure to be able to save that child.
Just before she vanished, Lain was full of hope."
And she went by like a tragic hero.
On a side note, look how this MC's power is unreasonable:
“What’s with you! It’s a sage’s divine protection, right? Or the Sword Saint? Or are you a dragon’s descendant? But what makes you able to do that! How do you kill things that are dead!”
“It is my job of deciding what is death. It is alive if it’s moving, and stops when it’s dead. I don’t care about what you would think.” (Yogiri) [ignore the second part and because it may lead to misunderstandings, he really chooses what's alive or dead by himself, ghosts? undead? sages or heroes? Pfft, you can all die.])
And I was like: OK, just here for the kills, I don't even know if I got everything right... I'm going to re-read this part and I'll come back to edit if I got something wrong or to organize, since I'm just writing anything that comes to my mind.
(Edit: See? I did as I promised! Now you have wasted your time reading a spoiler! Thank you for your attention, now you can proceed on what you were doing before being stopped by this spoiler!!)