November 4th (Scorpio)
Unnamed Parents (Deceased)
Rabbits, Tofu, Hydrangeas, Ghosts
Dogs, Thunder, Flies
Kyōka is a girl short in stature, with dark blue hair tied into two low twintails with flower pins. A notable trait of her (much like almost every member of the Mafia), is that before, her eyes used to be very dull. But after meeting Atsushi and being together with the Company, those blue eyes have been shown to become clearer. She always dons a red Kimono with pattern of what looks like sprouts, and its yellow Datejime neatly tied. She wears long white socks and sandals; while on her arms, she appears to wear yellow and red wrist pads. Kyōka carries with herself a tiny rabbit doll, together with her cellphone in a necklace.
While with the Port Mafia, Kyōka Izumi's personality is similar to that of a doll. She lacks all emotions and is ruthless when she is ordered to perform a duty. After being exposed to Atsushi and the real world, Izumi reverts back to a young teenager. She is easily infatuated with the small things and has a need to see everything. Much like Atsushi, she believed that she was worth very little and that she deserved to die for her crimes. Although unlike Atsushi, once she joins the Armed Detective Company she does not dwell on her mistakes. She is strong willed and even states that she wants to prove to Akutagawa that she is more than just a killer. Kyōka seems to care greatly for Atsushi. She shares a room with him and gets worried when he could be in danger. She is by Atsushi's side most of the time.
AbilityKyōka's ability, Demon Snow (夜叉白雪 Yasha Shirayuki?), allows her to materialize a sword-wielding phantom, known as Demon Snow, which only follows orders coming from a mobile phone she always carries on her person. It appears that it only listens to orders from another person on the other line and does not comply to Kyōka's own wishes. Though after joining the Armed Detective Company this problem was fixed by Fukuzawa Yukichi which enables her to control her own ability and use it normally. In reality Kyōka is not the original wielder of Demon Snow, but instead her mother was. In order to protect Kyōka, in her last moments Kyōka's mother transferred her ability Demon Snow to Kyōka -- but because of the suddenness at the time, control of the demon was transferred to Kyōka's cell phone instead of Kyōka herself.
According to Kōyō, before being an orphan, Kyōka supposedly lived happily with her parents. But ultimately, it was the Demon itself who killed them. It is also revealed that Kyōka's parents had a much darker background than previously thought.
Her father, after resigning from being a government agent, become a freelancer who worked for the assassinations of several important people. Her mother was, like her, an assassin who wielded the slaughtering ability Demon Snow.
One night, while Kyōka was out playing, several assassins came to try and kill both her mother and father. While all the assassins were quickly killed by the pair, an unknown ability user who could use body manipulation through blood took control of first Kyōka's father and used him to try and kill the young Kyōka. While Kyōka's mother had cut him down with Demon Snow before he could harm Kyōka, soon her mother was put under manipulation as well.
Before her death, Kyōka's mother transferred her ability Demon Snow to Kyōka in order to protect her, using a technique she had learned from an ability user who could manipulate shadows. However, due to the suddenness of the attack, the transfer of the ability was not perfect and so Kyōka's cell phone, given to her by her mother days before her death, became an intermediary for control of the ability. Since then, the Port Mafia took her, and she served under Kōyō Ozaki as her protegee.
Kyōka first appears in the city, seemingly waiting for someone. Soon, she spots her target, and uses her ability to apprehend Dazai, leaving him in Port Mafia's capture.
Afterwards, when Atsushi was out shopping with Yosano, they passed by each other without thought. but Atsushi notices her focus on him for a brief moment. Later on, on the train attacked by Motojiro Kajii, she encounters Atsushi once more, and Akutagawa orders her to protect the bomb on the train with her life, thus attacks Atsushi. After injuring Atsushi severely, she introduced herself as an orphan, listing her likes and dislikes, and confessing to her 35 murders within the span of six months. Their battle continues, but Atsushi soon deflects her. Kyōka shocks him, pointing out the last three victims were a family of three, and expresses little emotion. However, after Atsushi urges her to express herself, she wavers. She gives Atsushi the detonator to deactivate the bomb, but it is remotely force-activated after Akutagawa notices the button was pushed. Finally breaking from Port Mafia's influence, she attempts to sacrifice herself by jumping off the train with the bomb. Atsushi saves her and rips the bomb off of her, and the two fall into the river.
She wakes up in the Agency's infirmary. Atsushi and Kunikida persuade her to talk of the mafia's plans with tofu. Atsushi later shows her much of the city she never saw whilst in the mafia, showing her a new side of life. However, at the end of the tour, Kyōka intends to turn herself in to the police, aware of her unforgivable crimes, and that it is either imprisonment or mafia's execution awaiting her future.
Atsushi, however, is attacked by Akutagawa, who forces Kyōka to come with him. The three all depart on a cargo ship intended to take Atsushi to the people responsible for his bounty. Nonetheless, Kyōka intends to defy Akutagawa anyway, and sets a bomb off to sink the ship with her and Akutagawa with it. Akutagawa overpowers Kyōka and nearly kills her, but Atsushi saves her. After Akutagawa and Atsushi's showdown, Kyōka saves a badly weakened Atsushi from the sinking ship, landing in a rescue boat piloted by Kunikida.
Returning to the Agency, majority of the detectives celebrate Atsushi and Kyōka's success against Akutagawa, with Yosano and Naomi dressing her up in an outfit. However, when explaining her intentions of joining the Agency, Kunikida points out it won't be easy to deal with her and the crimes she committed, as many forms of authority will want her in their custody. She begs Yukichi Fukuzawa to let her join, saying she wants to prove Akutagawa wrong, that she isn't just a killing machine. After an intense stare down, Fukuzawa hires her.
Dazai arranges for Kyōka to room with Atsushi, both out of convenience and in favour of her safety against any mafia assassins who may attempt to kill her for abandoning them. Long after Atsushi and Tanizaki's run-in with Lucy Maud Montgomery, Kyōka runs up and hugs Atsushi in relief. Her relief is short-lived. Wearing civilian attire, Port Mafia's boss approaches an unsuspecting Atsushi, praising his efforts against Lucy, and walks away. His sudden appearance terrifies Kyōka to a trembling, speechless state that brings her down to her knees.
- The real life Kyōka Izumi was male, whose real name was Kyōtarō Izumi (泉 鏡太郎).
- In reality, Kyōka Izumi was the protege of Kōyō Ozaki and admired the latter throughout his entire life, pursuing a career in literature due to Kōyō.
- She appears to have photographic memory, often remembering people's faces and loads of information at a fast pace.
- She made an appearance in the mobile game "Kimito Lead Puzzle 18" as a stage boss and a limited time character.
- Her teddy rabbit was won by Atsushi on a claw machine.
- Kyōka is shown to be a skillful cook.
- Kyōka dislikes going to the toilet alone at night because according to her previous experience, private rooms like the toilet makes it easy to get attacked or assassinated.