The brother's diagnostic report mentioned a passage where the child had personally witnessed his father murdering someone in the bedroom and saw his father dispose of the body in the bathroom, before finally hiding the corpse in the kitchen refrigerator.
The three places mentioned in the report correspond to the younger brother's bedroom, the bathroom where the hair ghost resides, and the refrigerator hiding the headless body.
The younger brother's bedroom, filled with the highest number of ghosts and monsters, was the most dangerous; probably, the brother's subconscious was still affected by the memory of their father committing murder in the bedroom, making it the origin of danger and disaster for him.
The incessantly emerging hair in the bathroom might have been another scene the then-young brother witnessed, the father processing the body with strands of hair floating on the bloodied water.