Setsuna Imawano

Shizuru's sister, who used to be very close with her. She was a genius of the Jugondō, which made the head of the Jugondō, her father, feel threatened. He tried to have her assassinated and used Shizuru as a hostage, and so she disappeared, leaving Shizuru distraught but safe. She turns up when her father comes to Tokyo, and kills him immediately with the other members in a coup, leaving her in control of the Jugondō. She later attacks the Agency and kills most of the agents, except for Kagura, Kensuke, Kyouko and Iwahata. Setsuna is a skilled fighter, able to easily toy with Kensuke. She has the "Eye of Satori," a telepathic ability that enables her to read minds. As a consequence, one of her eyes is remarkably different from the other. She has a spirit beast, a water-using ogre-like creature called Suiko (Water Tiger). She is ruthless and ambitious, willing to kill her own sister and subordinates. Her goal was to set the world into eternal war. (Source: Wikipedia)