Mitsuba Sangū begins as a Special Duty Second Lieutenant in the Japanese Imperial Demon Army before defecting alongside her squadmates. A member of the prestigious Sangū family, she resents special treatment based on her name, believing it diminishes her accomplishments and imposes pressure to uphold the family reputation. She harbors a significant inferiority complex compared to her elite soldier older sister, Aoi Sangū. Her appearance features long blonde hair often in pigtails, purple eyes, and a notably curvaceous figure. She wears the standard Demon Army uniform: a long-sleeved black coat with gold buttons, a red bow tie, light green accents, epaulettes, and a Sam Browne belt, paired with a black skirt over shorts, knee-high black boots, and either black gloves (manga) or white gloves (anime). She sometimes adds a cape and always wears a white web belt with a gold waist-plate. A traumatic event at thirteen profoundly shapes her: the annihilation of her first Vampire Extermination Unit squad. Disobeying orders to maintain formation to save a comrade from a Horseman of the Apocalypse inadvertently caused the entire squad's death. This instilled a deep emphasis on discipline, rules, and maintaining formation, resulting in a serious, by-the-book demeanor. She exhibits intense frustration towards reckless behavior, particularly that of Yūichirō Hyakuya, and initially doubts Shinoa Hīragi's leadership. She is vocal and assertive in combat. Despite her strictness, Mitsuba possesses deep loyalty and self-sacrificial tendencies. Captured by vampires in Shinjuku, she urged her squad to retreat and leave her, directly linking this to her past trauma. She protects comrades, like shielding Mikaela Hyakuya. Within Shinoa Squad, she evolves, learning to trust her comrades' capabilities over rigid control. She develops a close friendship with Shinoa, eases into her role as second-in-command, participates in Shinoa's pranks, and shows empathy, such as understanding a rescued girl's false information given under duress. In combat, Mitsuba wields the Black Demon Series Cursed Gear Tenjiryū, a large battle axe manifesting at mid-to-close range. Its unique ability spawns multiple weak demonic entities as decoys or distractions when she strikes the ground. She demonstrates notable proficiency despite the axe's size relative to her stature. Joining the elite Moon Demon Company at thirteen signifies recognized combat talent. Her heightened strength, reflexes, and tactical awareness enable effective confrontation of vampires and Horsemen. She participates in key missions including Shinjuku defense, the Nagoya assault on vampire nobles, and later battles against threats like Ferid Bathory and Shikama Dōji. Reluctantly assigned to Shinoa Squad by Guren Ichinose, she gradually accepts her role and teammates. After Kureto Hīragi and Guren Ichinose betray and sacrifice their troops, Mitsuba defects from the Demon Army and her family, choosing loyalty to Shinoa Squad. This aligns her with the squad's actions, including uneasy alliances with former enemies like vampire Crowley Eusford against greater threats. Learning her parents were transferred to an underground facility adds personal stakes, driving her investment in Guren's controversial plan to resurrect humanity. She actively participates in supporting battles, such as fighting Fuola Honte alongside Mikaela. Interpersonal dynamics are central. Her relationship with Shinoa Hīragi evolves from initial irritation and leadership doubt into a strong, trusting friendship; Shinoa affectionately calls her "Mitsu." Interactions with Yūichirō Hyakuya start with intense dislike over his recklessness, reminding her of her past self, but shift after he saves her life in Shinjuku, showing signs of a potential crush with blushing and flustered denials when teased. She works cooperatively with squad members Yoichi Saotome and Shihō Kimizuki, the latter often cooking due to her acknowledged lack of culinary skill. Her relationship with sister Aoi remains complex, strained by competition, perceived inadequacy, and divergent loyalties after Mitsuba's defection. Internal conflicts revolve around guilt from her past, the burden of her family name, and seeking validation. She openly desires her family's approval, implying a lack of perceived love during her upbringing. Her character arc progresses from a rigid soldier haunted by failure to a more adaptable and openly caring member of a chosen family, committed to protecting her squad and resurrecting humanity for her loved ones.