[haguruma]

Originally Posted by Xellos-_^

the manga did reveal who "the other" is but there wasn't any clues in the manga itself for the readers.

Originally Posted by Doraneko

Then it sounds similar to the novel and it is my major disappointment.

Make no mistake. I still like the story as a whole (Mei = moe ) and especially the creepy parts, but I think it will do much better by ending in a different way.

Actually I have to disagree personally.

Spoiler:

There are several hints throughout the story if you go back and actually think about them in context.
Mikami-sensei is in charge of the arts department and while Reiko is an artist Kouichi has never actually been to her studio.
When Mochizuki said that he could walk home with Kouichi the latter felt very uncomfortable because they would get close to his grandparents home.
Everytime Kouichi is questioned about Mikami-sensei's "hotness" he doesn't know how to respond and merely says that it's difficult for him.
Everytime Kouichi and Mikami meet at the school their way of talking is very personal, down to Kouichi being surprised by her being at school so early.
Also the fact that Mikami-sensei is the only character of whom we never learn the first name.

I agree that it kind of lost its impact through the novels length alone. I assume the intent was to make every character equally mysterious...but even though it hinted strongest in the Reiko/Mikami direction it was hard to keep track of such small hints over almost 700 pages.
And the manga might have actually lost some of that, but that is because the artist seems to have choseen to make Mikami and Reiko look very much alike.

I don't really like it that they gave them different haircolours in the anime, but the hints are actually pretty strong. The one scene in episode 3 alone where Rei (the mynah-bird) is heard calling out "Good Morning Rei-chan, Good Morning" right when we see Mikami-sensei arriving. That was a rather clever transition.