Takashi Nishikiori

He used to be the leader of the pyramid group. He posed as a doctor to gain influence over others and used this to his own ends to make people work for him in return of letting them live. After coming to the island Takashi has turned into an evil man. A sadistic sociopath as well as a megalomaniac, Takashi takes a sick delight in torturing other physically, mentally, or emotionally, and has no qualms with targeting the weak or helpless, and seems to have a bitterness towards women. He uses fear to control people into doing everything he wants. He does not care for the well-being of his followers sending them into unstable narrow paths that could kill them. He later reveals he is not a doctor at all, but merely pretended to be one to gain power and sway over others - His medical knowledge all came from working pharmaceuticals.