Senkō attends Gessen Girls' Academy as a second-year middle school student. She possesses silver hair, green eyes, and stands 150 cm tall with measurements of B82-W55-H78. Her birthday falls on August 2nd, and she has blood type O. Battle serves as her primary hobby, while chocolate ranks as her favorite food. Her typical expression remains serious. She wears the standard Gessen uniform, featuring a longer skirt design exclusive to middle schoolers. Her shinobi transformation outfit comprises a dark purple and black suit layered with a short vest over a corset, gold accents, long sleeves adorned with losange plates, and a feather-designed waist cape secured by a gold belt. The ensemble includes slim-fitting dark purple pants and boots, embellished with pentagram symbols across multiple sections. A black headband decorated with small stars completes her combat attire. Initially, Senkō projects a facade of perfection to schoolmates, earning admiration as a model student and student council member. This veneer conceals her true nature: cold, brutal, and uncompromising in pursuing objectives. She harbors a fanatical drive toward justice but felt directionless alongside her half-sister Gekkō until discovering Kurokage’s diary in the school library. Adopting his extremist ideals, they sought to eradicate shinobi world corruption through violence. After losing a battle to Yumi, Senkō reevaluated her beliefs and embraced Kurokage’s "New Justice," prioritizing protection over destruction. Her closest bond is with Gekkō, her half-sister and tactical partner. They coordinate seamlessly during missions, though Gekkō occasionally teases Senkō outside combat—playfully touching her breasts or insisting on less revealing clothing. Senkō deeply admired Fubuki, whom they pursued using clues from Kurokage’s diary. Presenting themselves as Kurokage devotees, they became Fubuki’s subordinates to dismantle the shinobi world under a false banner of justice. Their loyalty fractured when Fubuki abandoned them after they questioned her methods, culminating in a failed confrontation where Fubuki defeated and stripped them. Senkō’s story opens with ambushing Hanzo Academy’s team alongside Gekkō. They captured all members except Asuka—left in torn clothing to instill fear. Under Fubuki’s direction, they organized the Shinobi Masters tournament, inviting rival schools under false pretenses to lure participants. After Yumi and Asuka defeated them in the finals, Fubuki publicly denounced all shinobi and discarded Senkō and Gekkō. The sisters later apologized to Hanzo’s team for their brutality, prompting Katsuragi to respond with inappropriate touching. Devastated by Fubuki’s betrayal and disillusioned, Senkō and Gekkō attempted suicide by leaping into a river. Yumi intervened, pulling them from the water and explaining her philosophy of justice as a balance between sword (strength) and shield (compassion). This spurred Senkō to adopt Yumi’s worldview. During the final battle against Fubuki, Senkō and Gekkō physically reached out to their former mentor to demonstrate Yumi’s teachings but were knocked unconscious by Fubuki’s yoma energy. In combat, Senkō specializes in high-speed close-quarters techniques using punches and kicks reminiscent of martial arts. She occasionally manifests a mysterious aura enabling limited ranged attacks. Her name, translating to "Flash," mirrors her combat velocity.