Kyōko Nagumo is the daughter of Zengo Nagumo, a candidate for prime minister in the film Zero Woman: Red Handcuffs. She is a young woman who becomes the central victim of a kidnapping plot carried out by a ruthless gang of ex-convicts. Her background is defined by her family's political ambitions, as her father is actively pursuing the highest office and has arranged a marriage for her with a wealthy businessman to strengthen his political position. Kyōko resists this arrangement and is shown meeting with a student activist shortly before she is abducted.

Her personality is initially portrayed as willful and rebellious, as she actively seeks escape from the rigid expectations of her father's world. However, after being kidnapped, she is subjected to repeated sexual assault, physical abuse, and forced drug injections, which reduce her to a helpless and traumatized state. She spends much of the story drugged and disoriented, stripped of her earlier defiance. Her character arc is bleak; after being rescued, she expresses a desire to die, overwhelmed by the violence she has endured.

Kyōko's role in the story is primarily that of a pawn and a catalyst. Her kidnapping is the event that forces the police to release the protagonist, Rei, from prison and send her undercover. She serves as a human shield and bargaining chip for the criminals, and her father's reaction to her ordeal reveals his true nature. When he learns she has been drugged and assaulted, he orders her killed to protect his political career, viewing her as a ruined asset. In the final scene, Kyōko is delivered alive to the police headquarters and locks eyes with her father from across the street, a moment that underscores her complete abandonment.

Her key relationships are defined by exploitation. Her father, Zengo Nagumo, treats her as a political tool and ultimately condemns her to death. The gang members who abduct her see her only as a means for ransom and as an object for their violence. Only the protagonist, Rei, takes any action to protect her, though their interaction is minimal. Kyōko shows little development beyond her initial rebellion and subsequent victimization; she is a character whose suffering exposes the moral corruption of the powerful.

She has no notable abilities or combat skills and is entirely dependent on others for her survival. Her significance lies in her status as a symbol of the collateral damage caused by both criminal savagery and political ruthlessness.