Kyōko Nakamura, widely known by her nickname Okyo or Marble Okyo, is a supporting character in the 1987 film Sukeban Deka: The Movie, which continues the story from the television series Sukeban Deka II: Shōjo Tekkamen Densetsu. She hails from a working-class neighborhood in Tokyo, specifically the downtown area, and her upbringing shapes her into a quintessential Edokko with a quick temper, a stubborn streak, and a strong sense of loyalty. Her background is rooted in the streets, and she carries herself with the brash confidence of someone who has had to stand her ground from a young age. This upbringing makes her both quick to anger and fiercely protective of those she considers her own.

Personality wise, Kyōko is headstrong, impulsive, and blunt. She does not hesitate to speak her mind or challenge others, including her allies, when she disagrees with them. However, beneath this combative exterior lies a deeply caring and reliable nature. She is described as having a big-sisterly demeanor, always looking out for her friends and willing to put herself in danger for their sake. Her loyalty is unwavering, and once she accepts someone as a comrade, she stands by them through any hardship.

Her primary motivation is the defense of her friends and the pursuit of justice, though her sense of justice is instinctive rather than ideological. She does not seek out conflict for personal gain but responds with fierce determination when she sees wrongdoing. In the film, she is drawn into the mission to infiltrate the island prison known as Hell Castle not out of a formal duty but because her friend Yōko Godai, the second generation Sukeban Deka, asks for her help. This highlights her personal code of loyalty over any institutional allegiance.

In the story, Kyōko serves as one of Yōko Godai's most trusted allies. She is the one who tracks down Yukino Yajima, a former partner, and convinces her to rejoin the fight. This act demonstrates Kyōko's role as a connector and motivator within the group, ensuring the team is complete for the dangerous operation ahead. She participates actively in the infiltration and combat sequences, contributing her unique skills to the overall effort.

Her key relationships are defined by mutual respect and shared battles. Her bond with Yōko Godai began with a confrontation during their school days, when she threw an apple at Yōko's head only for Yōko to catch it and crush it with one hand. This display of strength earned Kyōko's respect, and they became close friends. She also has a working partnership with Yukino Yajima, another ally from the television series, and the three of them form the core of the team that storms Hell Castle. Her interactions are marked by occasional bickering but an underlying, unshakeable solidarity.

Development is subtle but present. Kyōko begins as a street-smart brawler who acts on impulse, but through the course of the mission she shows a willingness to follow a coordinated plan and work alongside others for a larger purpose. She does not undergo a radical transformation but reinforces her existing traits of courage, loyalty, and dependability under extreme pressure.

Her notable abilities center on her trademark weapon: marbles. She uses glass marbles both offensively and tactically, scattering them under the feet of opponents to trip them or throwing them with precision to strike targets. This skillful use of marbles earned her the nickname Marble Okyo. She also possesses sharp physical reflexes and a seasoned fighter's instincts, honed through years of street confrontations. Beyond her fighting style, her expertise in coordinating with her teammates and her ability to rally others add to her value in combat scenarios. Though not as powerful as Yōko Godai's special yo-yo, her marbles are an effective and distinctive tool that makes her stand out as a memorable supporting fighter.