Shinoa Hīragi originates from the prestigious Hīragi family, conceived via artificial insemination using Tenri Hīragi's genetic material. Her mother died under unnatural circumstances during childbirth, disintegrating post-delivery. Like her older half-sister Mahiru, Shinoa endured extensive childhood experimentation involving daily procedures with scalpels and needles across her body, including her head and womb. These experiments were deemed failures due to her inherent demon Shikama Dōji's lack of reaction. Overshadowed by Mahiru's prodigious status, Shinoa was largely ignored by her family and lived isolated in her own apartment. Mahiru initially served as her sole caretaker but later subjected her to physical abuse and psychological conditioning to suppress emotions, fearing desires would invite demonic possession. This included administering a lethal drug to numb emotional responses, which Shinoa survived. Shinoa deploys sarcasm and dry humor, frequently teasing squad members like Yūichirō Hyakuya about his lack of friends or romantic experience. She displays apathy toward familial power struggles, blaming them for Mahiru's death, and rejects ambition—resulting in her low rank within the Japanese Imperial Demon Army. Her emotional detachment stems from childhood trauma, though she reacts sharply when mocked for her short stature, revealing a vulnerable complex. As leader of the Shinoa Squad in the Moon Demon Company, she employs calm strategy during missions, emphasizing teamwork and formation. An early mock battle loss underscored the gravity of leadership and consequences of error, deepening her commitment to squad safety. Over time, she forms genuine bonds with her team, embracing their self-proclaimed "family" dynamic and valuing human connections. She develops reserved romantic feelings for Yūichirō to avoid feeding her demon, eventually acknowledging them openly. Her personality shifts dramatically when possessed by Shikama Dōji, turning violent and ruthless, but she regains control and resolves to protect her squad. Physically petite and shorter than most peers, childhood Shinoa had shoulder-length ashen hair, pale skin, and piercing amber-red eyes, dressed in a dark sailor-style dress. As a teenager, her lavender hair is pinned up with a magenta bow and features side braids. Her standard attire includes a grey sailor-style blouse with teal trim, black skirt, dark blue knee-high socks, and white shoes. Combat attire consists of the Japanese Imperial Demon Army uniform: a long-sleeved black coat with gold buttons, light green epaulets, magenta bow tie, white gloves, thigh-high dark gray socks, and knee-high black boots. Casual wear resembles the uniform without gloves or bow tie, adding a white camisole over a long-sleeved shirt. Her primary weapon is the cursed gear Shikama Dōji, manifesting as a large black scythe with a green blade edge capable of effortlessly cutting lower-ranked vampires and deflecting noble-level attacks. Shikama Dōji also materializes as a volcanic demonic entity with a molten eye and detached claws. Shinoa shares a unique connection with the demon, requiring no training to master the weapon and feeling they are "one and the same." During possession, her eyes shift from brownish-orange to pale yellow with thin pupils, intensifying combat abilities to overpower foes like vampire nobles. Her experimental heritage enables survival of lethal conditions, including organ-destroying drugs. Key events include delivering messages for Mahiru to Guren Ichinose as a child, where she first encountered Mikaela Hyakuya. As a sergeant, she monitored Yūichirō during his suspension before forming and leading the Shinoa Squad. During the Nagoya mission, she protected Mikaela from the Japanese Imperial Demon Army, defected after Kureto Hīragi massacred troops, and escaped with Shinya Hīragi's aid. She reluctantly allied with vampire Ferid Bathory for mutual goals. After Shikama Dōji possessed her in Shibuya, she shattered emotionally but reclaimed her mind with Guren and Mahiru's help. She later supported Guren's human resurrection plan while remaining vigilant against Shikama Dōji's influence. Her relationships feature loyalty and teasing dynamics. She respects Yūichirō's determination, risks her rank to aid him, and supports his bond with Mikaela. She supervises Shihō Kimizuki and Yoichi Saotome, often teasing Kimizuki about domestic skills. Mitsuba Sangū, her second-in-command, shares a close yet occasionally contentious friendship, nicknamed "Mitsu" by Shinoa. She works under Guren Ichinose with a blunt rapport where mutual insults mask underlying trust. Her bond with Mahiru involved deep admiration and trauma from abuse intended to shield her from demonic influence. She initially distrusts vampires like Crowley Eusford and Ferid Bathory but later collaborates strategically.