Sorry your review took so long!
-I think the line in the first paragraph which begins, "Never was he..." sounds a little awkwardly phrased. I might rearrange it so that it flows better, saying something like, "He was never doing something spontaneous, in the spur of the moment, just because."
-I'm guessing that near the middle of the page where you say, "...in the Dark's blood..." you mean that plural, so it should be Darks'.
-I'm hoping that you explain at some point how the Darks can literally survive without hearts....
-I like the parallel of the first few chapters. Now, seeing this, it'd probably be okay if you left the "Never was he..." the way it is. My only criticism of this parallel is the fact that you actually repeated many of the same sentences, which is a little tedious. It'd be bet if you could find some way to keep it parallel, but still introduce new information, or a new perspective on things.
-When you're showing Otom's thoughts, you don't need both the apostrophes and the italics. Pick one or the other, but I personally think just italics would be fine.
-I don't understand the bit where it says, "...partway smoldering two streets away..." Is the town only burning two streets away from where the character is standing? What do you mean by partway? Is it partway smoldering or smoldering partway down the street? I'm just confused.
-"...axes and swords up until the hilt..." should be "up to the hilt."
-"...Otom gave when he looked into the unfamiliar eyes of his own," makes it sound like it's Otom's eyes he's somehow looking back into. I don't know if that was what you were going for here.
-"...breathing that showed as happy as a Dark can be..." should be rearranged to be more like, "....showed a Dark as happy as one can be."
-"...what seemed the inevitable layer of soot..." should be "what seemed to be..."
Okay, the main criticism I have for you isn't purely grammatical, but has more to do with the flow of the story. You have the tendency to use very flowery language which involves a lot of clauses. At times, this can make it hard for the reader to get through; I know I had to go back and read a few sentences two or three times before I understood how you wanted it to sound and what you wanted to say. I'd suggest simplifying the sentence structure at least occasionally, just to make it easier to read. For example, I was particularly confused by the sentence in chapter four which begins, "Hands that had the red from blood..."
In addition, while the parallelism is cool in the beginning, you can't logically keep that up. In order to keep with the realistic aspect, there is no way that the two leaders' speeches would line up like that, and then it just seems like the parallel nature is forced. I'd recommend keeping it in the first few chapters almost a as a prologue, but beyond that... Anyway, you have an interesting premise and a very good start. Keep writing!