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 Medicide, it seems that enemy, girl with dark-pink hair, let's name her Poison, 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 Poison had big sister before, its girl from Melting and Dead event, which looks almost like Poison, 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 Poison learned about that and planned get her revenge on Hareta, its like eye for eye, but in that case, Life for sister.