Remedy/theories

Sworn Enemy
IIt seems that Hareta had a enemy, and in the end, judging by one place which can be enable from interaction with Flask of Yellow Medicine, it seems that enemy, girl with dark-pink hair, let's name her Doku, killed Hareta, its can be proved by shorthaired Hareta's ghost, girl with creepy evil smile and of course, slayed parts of Hareta's body, judging by Poisoning Event this girl poisoned Hareta by bad medicine on purpose.

Motive of Poison is Revenge
It seems that pink-haired girl Doku had big sister before, its girl from Melting and Dead event, which looks almost like Poison but with glasses, probably culprit of her death is Hareta, who been in unstable mental state or Hare-chan just been in wrong place and wrong time, anyway Doku learned about that and planned get her revenge on Hareta, its like eye for eye, but in that case, Life for sister.

Brother's Guilt
In theory Hareta had a little brother, its a boy who jumping of balcony, judging by event with shadows probably he is main culprit, he can made massacre of Doku's family, especially her big sis, or he can kill his own lil sis Hareta, but its not passed easy for him, after that evil or psycho deed he felt guilt and decided atone his sin by making suicide.