I HAVE A THEORY!!!
This is for those who read the manga of tbhk.
Okay so what if Hanako/Amane asked Hanako-San(the girl) for a wish.
Think about it. Amane must have heard the rumor of Hanako-San and wanted to make a wish. He wanted to wish for Tsukasa to stop abusing him ( we all know that Tsukasa was the reason for Amane's bruises). Hanako-San grants Amane his wish, but the price was his brother's death. And since Amane knocked on Hanako-San's door, he is destined to die. Amane killed himself.Remember that if you knock on her door, eventually you're gonna die.
Does it make sense?