Yagyu hails from an ordinary shinobi lineage and shared an unbreakable bond with her younger sister Nozomi, who revered Yagyu’s commitment to ninja training. Nozomi succumbed to critical injuries from an abrupt car accident, leaving Yagyu scarred by grief. To eternally honor her sister, she wears an eyepatch fashioned from Nozomi’s ribbon over her functional right eye—a visceral reminder of the loss that first steered her into solitude and emotional detachment. Upon entering Hanzō Academy, Yagyu met Hibari, whose uncanny resemblance to Nozomi unsettled her. Hibari’s persistent cheer gradually drew Yagyu from isolation, forging a tight-knit bond where Yagyu adopted an overprotective older-sister role. This "sister complex" emerges from her terror of losing another cherished person. Though this friendship opens her to classmates, her protectiveness sometimes blinds her to Hibari’s capabilities. During the "Bon Appétit!" cooking tournament, Yagyu partnered with Hibari, initially lured by a wish-granting scroll prize to fortify their bond. Competing, she extended her sisterly demeanor to peers like Asuka and Daidōji, who sought familial ties. After defeating Hibari in the finals, Yagyu recognized their connection had deepened organically through shared trials; she destroyed the scroll, affirming their genuine tie needed no magical reinforcement. Physically, Yagyu stands 158 cm tall with white hair in twin-tails anchored by shuriken-shaped clips and crimson eyes. She fights with a bladed oilpaper umbrella and habitually snacks on dried squid—eaten barehanded—while accompanied by a giant squid guardian. A slight pot belly occasionally draws remarks from peers like Hibari and Mirai. Behind her stoic reserve, she harbors a dread of theme park rides, particularly roller coasters, which can fracture her usual composure. Her evolution across narratives traces a path from grief-driven isolation toward interdependent bonds, chiefly through devotion to Hibari. While inherently quiet and self-sufficient, her interactions reveal a growing readiness to rely on and shield her peers, balancing her ninja prowess with personal fragility.