Erika Chiba is the youngest daughter of the prominent magical Chiba family, born to the family head and his lover during his legal wife's illness. Denied the Chiba surname until entering First High School, she resided separately in a detached residence, fostering a strained relationship with her father. She has two older half-brothers, Toshikazu and Naotsugu, and an older half-sister. Her maternal lineage traces to Germany's Rosen family, which harbors resentment toward Japan stemming from her grandfather's elopement with a Japanese woman. Her appearance features distinctive short, bright red-orange hair often in a ponytail and lively facial features. She habitually wears figure-concealing clothing, rarely seen without it. Erika combines a cheerful, optimistic personality with a tendency to become easily carried away. She interacts in a friendly, familiar manner, sometimes perceived as overly casual or presumptuous, leading to frequent arguments. Close friends and brothers tolerate this straightforwardness. Past acquaintances recall her as cold, whimsical, or acting high and mighty, and she received romantic attention in school. She once talked to herself, a habit concealed upon entering high school. Elementary and middle school were marked by solitude; she formed friendships easily but neglected maintaining them. Rigorous training from childhood honed her reflexes and physical speed to exceptional levels. She developed the "Swordsman's Eye," enabling accurate assessment of opponents' capabilities and prediction of their movements. During the Watatsumi rescue, she deduced an adversary's affiliation with the USNA "Stars" unit based on fighting style. In systematic magic, her proficiency is combat-oriented despite broader limitations. She specializes in Speed-Type and Convergence-Type magic, utilizing Self-Acceleration for enhanced movement and Convergent Systematic Reinforcement to strengthen objects. Her signature techniques include Yamatsunami, a hidden sword method transferring stored inertia to a target, and its variant Yamatsunami Tsubamegaeshi. She also employs Kirikage, a non-systematic magic disrupting motor functions by targeting the psionic body, and Gram-Cut, a counter-magic neutralizing spells by severing magic sequences in the information dimension. Her equipment includes a weaponized-integrated CAD shaped as a telescopic steel baton, engraved with activation sequences by the Isori family. She wields Orochimaru, a specialized 180-centimeter blade designed for Yamatsunami. After Orochimaru proved impractical for daily use, she received Mizuchimaru, a downsized sword-type CAD adjusted for weaker Yamatsunami execution; it broke during a confrontation but remained functional for Kirikage. Relationships significantly define her development. She shares a pseudo-antagonistic yet close friendship with Leonhard Saijou, frequently bickering while denying peers' romantic suggestions. She trained him in sword-based magic. Her friendship with Miyuki Shiba involves mutual trust; Erika teases Miyuki about her relationship with brother Tatsuya, while Miyuki confides Tatsuya's secrets. Mizuki Shibata, considered Erika's best friend, senses Erika's potential romantic feelings toward Tatsuya. These feelings are implied: she expressed early interest, organized class support for him during a competition, and acknowledged his physical attractiveness. She resolved to pursue these feelings after discussing them with Mizuki, but halted upon learning of Tatsuya's connection to the dangerous Yotsuba clan and recognizing Miyuki's own feelings. She maintains a childhood friendship with Mikihiko Yoshida, teasing him while supporting his confidence. She bonded with Mibu Sayaka after initial conflict, visiting her in the hospital. She displays blatant antagonism toward Watanabe Mari, believing Mari unsuitable for her brother Naotsugu and criticizing Mari's influence on his swordsmanship dedication. Her development includes increased military recognition for contributions as a Chiba member, earning the moniker "Phantom Sword Princess of the Chiba." Her influence was evident when police complied with her civilian instructions during an island vacation incident. Combat experiences expanded through engagements like the Yokohama Incident, where her capabilities against adversaries like Benjamin Canopus became known among the Ten Master Clans. Personality assessments describe her as ambitious, competitive, fiercely independent, pragmatic, and organized, reflecting traits like duty adherence and attention to detail. Her loyalty manifests in protective actions toward friends like Miyuki.