Houko Byouinzaka

She is Yamane's elder sister and the professor's assistant, she is cold and heartless towards Iwai. She allowed herself to be Yamane's "Instead" as a way to relive her from the blood lust due to the pressure of killing goods that she possesses by allowing Yamane to inject her with a saline solution as a way to act out the latter's murderous intend. it is hinted that she has gotten so used to it, that she develops a kind of sexual arousal everytime Yamane does that sort of thing. Just like any participants of the " Murderer's Game" both she and Yamane also desires the wish that comes with killing the "Hair Queen" who happens to be Iwai. (Source: ANN)