Kunoichi operates as a fictional female ninja bodyguard within the narrative continuity. Initially an agent for Shingen Takeda, she receives assignments to protect Yukimura Sanada, reflecting her role in covert operations and combat support. Following Shingen's death and the Takeda clan's decline, she transitions into the service of the Sanada family, specifically aligning herself with Yukimura.

Her background identifies her as Shingen's adopted daughter, though this familial tie never diminishes her professional dedication. She maintains a steadfast protective stance toward Yukimura across numerous conflicts, accompanying him during strategic movements like his time as a political hostage to the Uesugi clan and fighting in pivotal clashes including the defense of Ueda Castle. During the Ueda Castle siege depicted in the animated special, she reports Tokugawa army movements to Yukimura and later provides crucial reinforcement alongside allies Mitsunari Ishida and Kanetsugu Naoe, directly influencing the battle's outcome.

Kunoichi demonstrates a blend of playful teasing and serious commitment to her duties. She engages in rivalries with warriors like the ninja Hanzō Hattori and the Uesugi retainer Kai, often framing conflicts as competitions. Despite her professional demeanor, internal conflicts arise concerning her personal feelings toward Yukimura, particularly during dire situations like the defense of Ōsaka Castle, where unspoken concerns for his safety surface against her sense of duty.

Her skills encompass espionage, infiltration, assassination attempts, and battlefield combat, primarily wielding dual kunai. She employs tactical diversions like setting fires during sieges and demonstrates agility navigating complex battlefields. A pet flying squirrel named Tsukimaru occasionally accompanies her, its role secondary.

Within the Sanada narrative focus of *Spirit of Sanada*, Kunoichi appears during Shingen's campaign against the Imagawa after Yoshimoto's death. After the Takeda collapse, she delivers Katsuyori Takeda's final letter to Masayuki Sanada before joining the Sanada clan permanently. She assists in rescuing the young Yukimura and other hostages during the Honnōji incident chaos, ensuring their safe extraction alongside the ninja Sasuke. Her involvement extends through the Sanada's strategic Sengoku period maneuvers, including resistance against Tokugawa forces.

Kunoichi's loyalty evolves beyond professional obligation into a personal commitment to the Sanada family's survival. She voices anxieties about Yukimura's safety before pivotal battles and continues her protective duties even when separated from him. Her interactions with allies like Kai reveal mutual respect forged through shared warfare experiences.