She is a tall thin lady with short curly hair slightly darker than her son's. The demon who possessed her assumes her form exclusively, never taking on a demonic appearance.
Susumu says that his mother used to be a nice woman, and the demon who possessed her is able to adopt this persona when it suits her, but like most demons, she is cruel and sadistic.
After being possessed, she makes Susumu's life a living hell. Whenever her husband is away, she locks Susumu in a small room and beats him. She later purchases a demon possessed dog she names Jiro for the purpose of attacking him as well.
One night at a park, Susumu finally reveals to his friend Tare the extent of his mother's abuse, and Tare offers up his home to him. She intercepts the two boys on their way to Tare's house along with Jiro. Tare confronts her, but she laughs it off. She claims that Susumu is a lonely child and so makes up stories about being abused as a way to stay over friends' houses. Not wanting Tare to be hurt by his mother, Susumu falsely confirms her story and goes home with her, leaving a confused Tare behind. She lies that his father has come early to give him false hope, as she only hurts him when his father is away.
Once home however, she begins to attack him for telling, and a terrified Susumu runs screaming through the house. At that moment, his father comes through the front door. Susumu runs to him, but it turns out that he too had been possessed by a demon. The three of them, husband, wife, and dog, then proceed to tear Susumu to pieces.