Lady Oyakata (お館様 Oyakata-sama), referred to Ruby as "My Lady", is a century-old witch that lives on Witch's Knoll and Ruby's guardian. She bears a great contempt for humans, as she and her fellow witches of her time have suffered through a long period of humans expanding their terriitory, and seeks revenge against them by destroying the city nearby with her army of monster plants after land developers attempt to turn her home into a garbage dump. Despite Tsukune's pleas for him to help her, she refuses to allow anyone to further harm her home, and tried to kill Moka until Tsukune removes her rosario while going through an army of Hanabake plants. During her fight with Inner Moka, she uses a forbidden spell to merge herself with the Hanabake plants. Although she gains the upper hand in battle absorbing Moka's vampiric powers, she was in a brief state of shock when Ruby injures herself while blocking the finishing blow that was meant for the latter, and absorbed her to gain her powers. She was soon defeated in battle when Moka impales the crystal in her spellbook with Ruby's wand, and was killed in the following explosion. While she was being whisked away by Ruby in a dream, she admits her true feelings to her, saying that she did not want her to be taken away from the humans.

In the Anime adaptation, she dies prior to Ruby meeting the Newspaper Club, but saw the errors of her ideas of revenge on humans beforehand. Her body still remained in their house as Ruby's mind fractured after being unable to cope with her death; a split personality used her image to relay orders to Ruby. However, her spirit is assumed to have been what saved Ruby from dying in the explosion of the monster plants and safely kept her above the waves of the ocean until Gin and the Bus Driver found her.

Much of Oyakata's magic revolves around flora, and she can extend vines from her fingers to use as an offensive weapon. Like Ruby, she can use ravens as familiars to serve as messengers. When fused with the Hanabake plants, she gains the ability of regeneration, rendering any physical attack useless. She can also absorb other living creatures and gain use of their abilities. However, the spell is considered to be a last resort; once transformed, she cannot revert to her former state.