Haruko Kimiyoshi

Kimiyoshi Haruko is the mother of Kimiyoshi Natsumi and the wife of Kimiyoshi Tōji. She first appears as the antagonist of Onisarashi-hen, but later it was revealed that she's innocent. One day, after arriving home from school, Natsumi saw her grandmother being attacked by Haruko. In the end, the grandmother dies. Haruko suggests cutting her into small pieces, so they can hide her better. Later, when the body is found by the police (this is advertised on the news), Haruko beat up her husband for hiding it improperly. After she left the room, he told Natsumi to call the police, but Haruko overheard this, returned and stabbed him, and decided she must kill Natsumi as well. Akira calls Natsumi's home and hears her screaming for help. When he arrives, Haruko knocks him out with a vase to the head, but is then killed by Natsumi. It is later revealed that this was all a delusion brought on by trauma, and that Natsumi was the one who killed everyone, and Haruko is presumably innocent. (Source: Higurashi No Naku Koro Ni Wiki)