[totoum]

Originally Posted by DesuX2

Well, I don't know according to Mei, the clause that she describes in the last episode

Thanks,I can see where you're getting at, when Mei says she uses the word "altered" figuratively I think she means that it's not someone who comes in and changes the documents manually.
Indeed "change" is a pretty vague term,there's lots of ways to change something.

Spoiler for To be honest:

I think he was just having a memory lapse. Because he's so distant from his son and busy with his work and all.

I'd say that if it were indeed just some trip,but the way the father said it seemed to imply he had lived there all his life until 18 months ago.

How does it feel to be back after a year and a half away from Yomiyama

It's one thing to make a mistake about when your son last visited a village,it's another to make a mistake about where he lived his first 13 and a half years of his life.
Or the translation is again misleading.

I'll get to the rest of your theory a bit later,maybe in another post.Right now I want to adress some things Skyfall brought up.

@Skyfall

First off I want to add another thing that could be a clue to Reiko beeing the "another":Kouichi's father has a couple times asked him to tell grandpa and grandma he said hello,never does he mention Reiko,who is supposed to be in the same household.

Originally Posted by Skyfall

there is the obvious issue of Reiko not being a student of the class 3, but I think this episode actually subtly and cleverly refuted that being a necessary requirement as well

I think sudents know this,Izumi said she had checked to see if Kouichi had any siblings,I think she did that because she would consider a sibling as a suspect.

Originally Posted by Warita

But if we asume, that the extra dead person can appear outside the cursed classroom, why would they be short on one desk? This part doesnt make sense, because obviously there is one extra student in the classroom. Not an aunt who sits at home all the time and complains about headaches.

Kouichi acts as a proxy?The curse didn't take affect until he transfered in which meant the class was short of one desk.So while Reiko would be the "another" it's Kouichi's transfer that acts as the trigger.