Kuroki first appears as a fighter employed by the criminal Mr. Big, working as a bouncer in his establishment. Her early depiction presents her as a male Muay Thai practitioner from France, later revealed as a deliberate disguise to establish fighting credibility and conceal her identity. She confronts the protagonists during their raid on Mr. Big's organization while they search for a kidnapped family member. Defeated in combat, her true gender is exposed. This encounter prompts her to aid the protagonists by supplying information leading to Mr. Big. Her motivations subsequently shift toward entering a martial arts tournament to win prize money for a critical medical operation for her younger brother, Jan, who requires surgery to regain leg mobility. Acknowledging her prior assistance, the protagonists pledge their potential tournament winnings toward Jan's surgery. Her visual design evolves in later appearances, integrating more feminine elements while largely preserving her original concept as a fighter who initially masked her gender.