Awazumi Hospital

Awazumi Hospital is a hospital in Hokkaido. On Wednesday January 14th, 2009, Inubushi Keiko killed 12 patients and wounded 19 others. One of the deceased was Yomogi Junichi who had been hospitalized for a bicycle injury.

Description
Inubushi Keiko, who was 17 years old at the time, used half a pair of pinking shears to kill the security guard to enter the hospital. Her attacks began at 4 AM and continued for nearly half an hour.

A doctor went into a room to find two bodies on beds, one of which had its chest ripped open. The patients heart had been thrown against a wall in the corner of the room. A patient with a slit throat grabbed the doctor's leg and say "The shadow... has come..."

Eventually, Inubushi was cornered on the rooftop by police and arrested. Before her arrest, she dropped her blood-stained blade and asked "Where is Self?". She remained silent during the following investigation. Despite searching for the other half of the scissors used as a weapon, it was never found.

Aftermath
In the end, Inubushi was found innocent due to her suffering from Dissociative Identity Disorder. As of 2011, she was held in SPHIA, short for "Specified Psychiatric Hospital for Isolation and Aegis".

Utsumi Kali's mental health deteriorated as a result of the murder of her child. She was placed in mental healthcare institutions and eventually finds herself in SHPIA with Inubushi in 2012. Utsumi uses this opportunity to exact her revenge.

Motivation
While Inubushi's motivation is never explicitly stated, she killed a rat in SPHIA with her bare hands. The rat had been poisoned by the MAO inhibitor with little chance of recovering. She justifies herself by saying she ended the rat's suffering. It is possible that she killed the patients to end their pain as well.