Okay, here's my crazy theory on how the end will play out based on what we know as of episode 10 with only two more to go. Note that this is 100% PURE SPECULATION as I have managed to stay
completely spoiler free for this series and intend to keep it that way for the remaining two weeks. I'll spoilerize it anyway, just to be on the safe side.
Spoiler for SPECULATION:
After a series of gruesome events and a high body count due both to the calamity as well as people going crazy looking for the Another, Akazawa is revealed to be it (explaining why hers and Kouichi's memories of meeting before have been erased - he knew she was dead. Hey, they have to pay that off somehow, yes?). Eventually, she dies somehow (possibly she takes her own "life" to protect her classmates after discovering the truth) and the calamity is averted for the rest of the school year.
Except, there is one final victim - Kouichi, who dies (due to events already in motion, like, say, his lung illness or whatever - hey, they have to pay that off somehow, yes?) after accomplishing some important task or plot point. His friends mourn him, very sad.
Flash forward to present day (hey, they have to pay off the "1998" thing somehow, yes?) and we're introduced to this year's new class 9-3. We see images and possibly are told the names of a select few of the students, ending with... Kouichi Sakakibara. Dun dun dunnn.... End.
And if I'm wrong about the identity of the Another, then it really could be anyone. That is, anyone except Kouichi or Mei - if it turns out it's either of those two after all, then that will have been the biggest cheat ever.
(Attention book/manga/wikipedia readers: Please do not comment. I do not want to know if my theory is close, right on the money, or way off.)