Akiko Yosano operates as the Armed Detective Agency’s chief physician, wielding her unique healing ability, *Thou Shalt Not Die*, to revive members teetering on the brink of death. The power activates solely under near-fatal conditions, compelling her to deliberately inflict severe injuries—often via chainsaws or axes—before reversing them, a method that unsettles even her battle-hardened peers. Born December 7, she spent her youth laboring in a confectionery shop until Ōgai Mori forcibly recruited her at age eleven during the Great War. Stationed on Tokoyami Island as a military medic, she mended countless soldiers, earning the moniker “Angel” for her lifesaving efforts. A surviving soldier once gifted her a golden butterfly hairpin in gratitude, a token she still wears. Yet the relentless cycle of patching soldiers only to return them to slaughter fractured her psyche, exacerbated when a traumatized comrade branded her the “Angel of Death” before taking his own life. The ensuing breakdown drove her to scuttle her ship, resulting in imprisonment and postwar seclusion. Rescued three years later by Ranpo Edogawa and Yukichi Fukuzawa, she joined the Agency. Ranpo’s insistence on valuing her compassion over her ability reshaped her identity, transitioning her from wartime instrument to guardian of life. Her past fuels her vehement opposition to those who trivialize existence, such as Motojirō Kajii, whom she openly challenged for his cavalier attitude toward human worth. She sports a dark bob-cut hairstyle accented by the golden butterfly hairpin, magenta eyes sharp with wit, and attire blending professionalism with flair: a white blouse, black skirt, and crimson heels. Her demeanor oscillates between poised elegance and biting intensity, particularly when countering sexism or recklessness. Key arcs test her convictions. During the Agency’s public framing as terrorists, she led peers in tactical gear and prison uniforms, maintaining resolve amid chaos. A confrontation with Michizō Tachihara of the Hunting Dogs—who hinted at shared wartime ties—pushed her to reaffirm her oath to protect life over vengeance. Her ability’s name draws from feminist poet Yosano Akiko’s anti-war verse, mirroring her narrative role in condemning exploitation and upholding life’s sanctity. This literary homage reinforces her stance against cycles of violence. Her relationships remain fraught: an entangled history with Mori, who sought to militarize her gift, contrasts with Ranpo’s recognition of her humanity. She mentors younger agents like Atsushi Nakajima and Kyōka Izumi, guiding them to reclaim self-worth amid trauma. Beyond duty, she indulges in Japanese sweets, shopping excursions, and spirited drinking sessions, often dragging colleagues into her pursuits. A fusion of empathy, tactical ferocity, and morbid humor, she anchors the Agency’s ethical core while navigating its darkest battles.