Hayabusa, a ninja of the Koga clan and sibling to Kojiro, witnessed their parents killed by the immortal cyborg Ginnai Doma a year and a half before the main events. Though burning for immediate vengeance, Hayabusa reluctantly obeyed Kojiro's command to prioritize retreat during their village's attack. Characterized by pragmatism and emotional restraint, Hayabusa openly criticizes perceived weakness, rebuking protagonist Shishimaru for mourning a fallen comrade. This clash creates friction, prompting Shishimaru to dismiss her clan as "loud women." Her combat skills prove formidable during coordinated assaults on Ginnai. In one infiltration, she joined Kojiro's team ambushing Ginnai in his sleep with poison darts and blades. Though Ginnai survived and counterattacked, Shishimaru intervened to save Hayabusa from a fatal blow. Hayabusa's development shifts from detachment to deeper alliance. After elder ninja Nagatoji sacrifices himself to delay Ginnai, his dying words entrust Hayabusa to Shishimaru's care. Demonstrating increased cooperation despite prior conflicts, she later participates in a tactical trap against Ginnai involving explosives and rock slides. In the manga continuity, Hayabusa operates as a 23rd-century time-traveling agent. She journeys back to the Sengoku period with allies Burn Mano and Jimmy Rocca to confront distortions caused by Nobunaga Oda's anachronistic technology. Captured and subjected to mental interrogation by Nobunaga's forces, she is later rescued. Witnessing the near-destruction of her allies, she joins Shishimaru and the extraterrestrial "Black Lion" faction to combat interdimensional threats. Following Ginnai's defeat in both storylines, Hayabusa departs with Shishimaru and the Black Lion entities, transitioning from personal vengeance to a broader role safeguarding the universe.