Kana Kusakabe is assigned to investigate the serial rapist X. However, information on X is extremely limited, and even his name remains unknown. Kana's father, Gorou Kurosaki, was also involved in the investigation but died before completing it. Kana asks Eiji Kagami, her father's former subordinate and the man believed to be closest to X, for assistance. But Kagami himself is actually X. He develops a strong obsession with Kana, uses drugs to manipulate her consciousness, and begins a new game.