Okay just finished reading and I must say, very satisfying ending.
Honestly most of the people from the village were absolute trash who couldn't reflect on themselves, so it was a relief that they got what they deserve in the end. The more the story advance, the more you realize that they are binded by their stupid beliefs and that they are in fact most inhuman (they are ready to kill whatever doesn't fit in)
Obviously I'm not excusing the Shikis either, they remain the villagers that they were before and carry on their sins and personality so their downfall was most satisfying (especially Megumi).
I was kinda disappointed with Natsuno, his response to all of this was just to kill all the Shikis but well if there is no Shiki left alive I guess so are the problems. However by that logic he might as well kill all the villager because they brought this upon themselves by killing eachothers (They could have just accepted death but they chosed to embraced their own nature, not that they are wrong doing so)
Overall I think the point of the author was to make a critic on human expectations and moral values, by showing that Shiki/Human doesn't actually really matter but it reveal the nature of people. Being a shiki is perceived by others by a sin in itself (once again because it threaten the village/ human society belief), and the shiki is forced to bypass the rules previously established if they want to survive.
Now for Sunako and Seishin. In Sunako words "Death is equal to all" and we're all equal before death, I don't see why she needs to die because some other people want to survive, it's her right to want to live and for that she need to kill people. That's exactly what are doing the villagers at first by eradicating the Shikis, they want to survive. The bond that she shares with Seishin is based on their similar condition : they didn't wish for it but they have to bear with it. I admit that the point defended by Seishin is wrong, they remain human ; but they try to escape from being a simple gear on the human machine whithout questioning it . I actually like that about them, the fact that they don't judge someone only by their condition and the role attributed to them.
Truth is, Sunako and Seishin are trapped. They won't ever be able to fulfil their dream of a society where you can leave the place where it was decided you belong to and be accepted. As Tatsumi implied if there was a scenario where Sunako suceeded to make the Shikis more numerous than humans to live without being rejected, the lack of blood would make them wither to extinction.
So rest assured if you resented them, in reality nobody won.