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Character:

Her name and appearance hint at her being connected to Miyo Takano from Higurashi leading to the possibility that the game she played with Bernkastel was the world of Higurashi with the battle between Rika and Takano being the purpose of the game.She is the most powerful witch next to Bernkastel,and is feared by most other witches, including Beatrice.Her Magic of Certainty allows her to kill anyone without fail as an absolute result,which bends the basic rule of Umineko magic requiring a risk.

Source from Wikipeida