Crazy Kenji conspiracy time!
I'm probably gonna look stupid after writing this but this is all to get your minds going!

So you know how whenever you mean Hanako, she seems extremely nervous about talking to Hisao?
It's just assumed that she's like that with everyone, and that she is shy.
But no one knows her story. Not even Lily fully understands.
It starts off with her sneaking around class with Hisao around, and when he confronts her, she runs. She is very nervous about telling her story around him and even when she does tell him, she gets nervous and usually stops herself.
This is possibly because she has to work around a few kinks in her story that truly reveals who she is.
We all know Hanako has earned her scars from the burning of her house. But SHE always seems to take responsibility for it. Who's to say she didn't intentionally burn her house to kill herself to her own depression? Possibility from another chain of events she caused herself? It says that the only reason she didn't die is because he mom shielded her. Maybe at the instant she was to die, she managed to realize it wasn't worth it.
Is it also not fishy that she seems to instantly fall in love and be very shy around Hisao?
Iwanako is the girl that caused Hisao to have a heart attack when she confessed her love. She visited him for a long time but things got silent and awkward. Very similar to how Hanako is around him (at first). So eventually Iwanako stopped visiting Hisao, which assumingly leads to depression.
Who's to say she didn't burn the house down?
Do you seen any ODD connections?
Isn't it ODD how Hanako seems to instantly draw towards Hisao and blames herself for the house fire and all?
Now there's a few errors in this.
You may say:
No way, Hanako was said to be there for awhile!
Well you also have to remember--- no one at all notices Hanako due to her "shrinking" type vibe. Who's to say she didn't just suddenly enter the school and tell everyone she's always been there?
It's a far fetched idea but not by much.
Miki, the side character also plays quite a role in this. She talks about Hanako like she's some kind of monster. Miki never explains her relationship and how she knew Hanako, we just know they're not fond of each other.
What if Hanako explained how she gave Hisao the heart attack and burned her house down?
You may also say that Hanako had to have been in the ICU (Intensive Care Unit) for quite some time due to her burn scars. But her scars are still VERY VERY noticeable and don't look like they've had much time to heal.
Maybe she wasn't in for long and she got out before Hisao?
It's all a crazy idea and probably not true.
But at the same time its not so far fetched.
Hanako could be Iwanako. Now, discuss.
If you have further question to my theory. I will gladly answer.
I'm also a HUGE Hanako fan, so i'm not saying it's true. Just very odd how it's all layed out.