Kyouka Izumi is a teenage girl with dark hair typically worn in low twin-tails secured by flower pins and clear blue eyes, a change from their previously dull appearance during her time with the Port Mafia. She commonly wears a red kimono featuring a sprout-like pattern, a yellow datejime belt, long white socks, sandals, and yellow and red wrist pads. She carries a small rabbit doll and a cellphone on a necklace, the latter originally crucial to controlling her ability. Born on November 4, she stands 148 cm tall, weighs 40 kg, and has blood type B. Her parents were assassins; her father worked as a freelance government agent, and her mother wielded the ability Demon Snow. Assassins attacked their home while Kyouka was playing outside. Her parents killed the assailants, but an enemy ability user manipulated her father through blood to attack her. Her mother used Demon Snow to kill him but was subsequently controlled. In her final moments, Kyouka's mother transferred Demon Snow to Kyouka for protection. The abrupt transfer linked control to Kyouka's cellphone instead of her will. Orphaned, she was taken in by the Port Mafia. Within the Port Mafia, she served as a protégé under Kōyō Ozaki and became a notorious assassin nicknamed the "Thirty-Five Count Murderess" for killing 35 people in six months. During this period, her personality was emotionless and ruthlessly obedient, resembling a doll. She believed her life held little value and deserved death for her crimes. She once sought Ryūnosuke Akutagawa, hoping his ability could destroy Demon Snow and end her life, but he instead gave her a purpose through killing. Her path changed after encountering Atsushi Nakajima during a train bombing mission. Ordered by Akutagawa to protect the bomb, she fought Atsushi but hesitated when he urged her to express genuine emotion. She defected by giving him the detonator, though the bomb activated remotely. Attempting to sacrifice herself, Atsushi saved her. Awakening in the Armed Detective Agency's care, she intended to surrender to authorities. However, after Atsushi rescued her during a confrontation with Akutagawa on a sinking ship, she requested to join the Agency. Director Yukichi Fukuzawa accepted her when she declared her desire to prove she was more than a killer. As an Agency member, she roomed with Atsushi for safety and gradually adapted to ordinary life, developing typical teenage interests. She displays a fondness for tofu, crêpes (often given by Atsushi to cheer her up), and sweets shown by Ranpo Edogawa. She dislikes dogs, thunder, and flies, and avoids using toilets alone at night due to assassination fears. Despite her growth, she retains a complex morality, willing to harm others or become a criminal to protect the Agency. She practices non-lethal combat but acknowledges the difficulty of breaking her lethal instincts. Her ability, Demon Snow, materializes a sword-wielding phantom. Originally, it obeyed only phone commands from external parties (typically Port Mafia handlers), ignoring Kyouka's will. After joining the Agency, Fukuzawa's intervention during the Guild arc resolved this limitation. When the Guild threatened Yokohama, Kyouka was captured by military police. Aboard a drone, she spoke with Osamu Dazai, who convinced her not to abandon hope. Choosing to sacrifice herself by crashing the drone into the Guild's airship, Moby Dick, she passed the Agency's entrance exam through this selfless act. Fukuzawa's ability then activated, allowing her direct control over Demon Snow. She escaped by using the ability to sever her restraints. Later investigations revealed Demon Snow did not kill her parents; it was a manifestation of their love protecting her, allowing Kyouka to reconcile with her ability. Beyond her supernatural power, she demonstrates exceptional physical skills including acrobatics, swordsmanship, infiltration, lockpicking, disguise, and driving. She possesses a photographic memory, memorizing extensive lists, maps, and building layouts quickly. She also has knowledge of anatomy and acupuncture, the latter used strategically during missions. Her relationships define key aspects of her development. Atsushi Nakajima remains central, symbolizing her "light" and offering unwavering support. She relies on him emotionally, trembling in fear upon seeing the Port Mafia boss near him. Kōyō Ozaki, her former mentor, represents her dark past and occasionally attempts to draw her back into the mafia, though Kyouka consistently rejects this. Fukuzawa's acceptance and ability to stabilize her power solidify her loyalty to the Agency.