
So, the whole point of this manga is a basically...nothing. Or is it? lol I'm going to take a crack at making sense of this:
1) The drawers were haunted and when Rin opened them he basically cursed everyone with insanity or false memories or something. I'm not sure how that would explain his dad, though, as his dad wasn't there with them. Unless, it was Himeko and Yama imagining Rin's dad saying those things and praying to Himeko. Basically, everything shown is a mindf*ck based on the premise of "is this really happening" and "what's real". Like I said, insanity.
2) The drawers are cursed or possessed by an entity and whoever comes into contact with the drawers remember the entity as a different person. Again, this doesn't really explain Rin's dad nor does it explain the bit with the teacher or why the other student could see what was happening.
3) Sakiko is a ghost messing with everyone. Again, doesn't explain the dad.
4) Sakiko is really Rin's mom and is haunting them/messing with them and driving everyone crazy. This would explain the dad, but wouldn't explain the drawers out in the middle of no where. Unless the drawers are just a red herring and everyone was crazy before they found them. Sakiko may also be messing with Rin (and the others, by extension) out of revenge for her death, blaming Rin for her death. This could explain why the dad is exempt from the madness but doesn't really explain the last page.
My guess is #1. I think the whole point of this manga is to mess with our heads and question what really happened and what's going on. And that's it. It's probably best not to think too much about it. Your brain will symbolically explode like Rin's.

Well, I think the point is to let us see how scary it is that our brains are run by electric signals and how (potentially) easy it could be to mess with. It wasn't really conveyed well (but it could've been!), so sensei had to resort to text at the end (to "explain"). Just my two cents!

Haha, omg. As mean as that was, I can't help but think Zhang did that to the girl's letter to make Jian happy. (≧∀≦)

NO. Because that would only make Jian Yi feel miserable and anxious. He doesn't want people to fancy XiXi, and would dislike if Xixi becomes even more popular, and students begin to surround him all the time to gossip. Also, he would feel guilty if the girl was humiliated like that, especially when it's clear Xixi doesn't correspond the girl's feelings, so there is no need for such cruelty.

And some people think Levi will die in the main series? Not gonna happen. He gets his own spin off series and many, many readers will rage if he's killed. It's probably in shoujo manga because Levi has so many fangirls. ╮( ̄▽ ̄)╭

Isayama sensei is writing a horror manga series, this is not the typical case where good characters live and bad ones die, tihs is a much bigger work than that, this is like reality.When the time comes, though it'll break many hearts including mine, if Levi has to die, the mangaka won't hesitate.

your thinking of tragedy, which attack on titan also is, but that's beside the point
in horror alone, people can needlessly die, but the main characters are safe, it becomes tragedy when main characters can also be killed/are killed, which can be separate from horror and apply to other things, though generally horror will always involve tragedy, not necessarily the other way around... i guess think game of thrones in that sense, but anyways
i think the mangaka would hesitate, there's probably a lot of people that would drop the manga/anime if levi died, at least that being my guess given his ridiculous amount of popularity, and if people drop, they'll lose money, and that's where the mangaka's writing is going to go towards, almost always, that's pretty much a given, and it doesn't look like this author is george r. r. martin, pretty sure that guy gets off on killing peoples favorite characters... but i think even he'd have to bend to certain pressures of his audience sometimes
aside from that though, isn't levi kinda... too bad ass to die? i just don't feel like there would be an easy or simple way to kill him, even if people were plotting to kill him in some complex scheme that hinders his abilities, it almost doesn't seem possible with levi, i could only see him dying towards the very end as a sacrifice of some sort, and even then, it still feels like he'd still somehow turn out on top...

Exactly! Writers very rarely kill off favourite characters, especially ones as big as Levi. There is a lot of pressure from editors and publishers to avoid pissing readers off (I work in the publishing industry, so I know: readers come first). And I agree: it would take a lot to kill off Levi. In fact, I wouldn't be surprised if he was the last one standing at the end.

i also completely forgot, his name is derived from "revive" (can't remember the language(s) though), it'd actually be pretty cool if we see the author take that play on words and make it real
in that sense, i could definitely see the author killing him, if only to bring him back somehow and make his name more literal
Lol Rood. That's a move Shic would pull XD
No wonder Shic fell for him. lol.