Misaki Aoyagi

She is the mother of Seimei and Ritsuka. She has an important influence over her sons. Being emotionally and mentally weak, Misaki has very little grip on reality, and often hallucinates, particularly after certain events in volume 5. She is abusive and violent and blames Ritsuka's personality change for the reason Seimei "left", demanding that she wants her former Ritsuka back when she beats him. To many, she is seen as a cruel villain, but in volume 5, she has inner dialogues of her own, allowing the reader to witness a more human, fragile side to her behavior which she cannot control.

(Source: Wikipedia)