Suiyan
I agree with Craigy's last paragraph at least. It's true, now that you made me remark it, that it should be an at least difficult thing for Rean to kill. Even though, strictly speaking he didn't deal the final blow, their powers should have some kind of restrictions too. Like how their presence affects the environment's balance (their village is the exemple) we could see the consequences of their powers' existence. HOWEVER! I'm not saying I want a non-kill Rean. Please anything but that.
Not the biggest fan of this arc. So far, the two protagonists have acted in a mostly morally upright manner and primarily killed bad guys. However, in this scenario, they are actively working to generate conflict in order to seek out people to kill. Not only that, but they’ve worsenned a war needlessly. You can argue that they couldn’t predict the effects of their actions, but considering how intelligent they’ve been in every other scenario I highly doubt they wouldn’t predict this outcome. Furthermore, the argument that the war would get to this stage without their intervention is total BS. There is no way to predict the outcome of a conflict with a 100% certainty and their actions made a peaceful resolution much less likely. This whole arc is completely completely out of character for Rean who has so far only killed for the right reasons. I’m honestly not sure why the author decided to make him into a murder hobo, especially considering he is supposed to embody LIFE.