Kyōka is a short girl with dark blue hair that is tied into two low twin-tails with flower pins and blue eyes, in which a notable trait of her, (much like almost every member of the Port Mafia), is that before, her eyes used to be very dull. But after meeting Atsushi Nakajima and being together with the Armed Detective Agency, her eyes have been shown to become clearer.
She always dons a red Kimono with a 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 attached to a necklace.
While with the Port Mafia, Kyōka'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 Nakajima and the real world, Kyōka reverts back to a young teenager. She is easily infatuated with 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 and at a certain point in her life, was filled with so much vengeance towards her own life that she wished to be destroyed along with her Ability. Although unlike Atsushi, once she joins the Armed Detective Agency she does not dwell on her mistakes and tries her best to be useful to her comrades even if it means harming and killing others for their sake.
Kyoka is quite apathetic and strong-willed, she even states that she wants to prove to Ryunosuke Akutagawa that she is more than just a killer. Kyōka seems to care greatly for Atsushi to the point she would threaten to cut down anyone who was a harm to him. She is later seen trusting his skills more and letting him fend for himself.
Kyoka has a shaky sense of morality in which she believes it is alright to become a criminal or harm/kill her opponents in order to preserve herself and the Armed Detective Agency, which is similar to the morality of a lot of her colleagues. She can also be quite vengeful as she was not above killing Akutagawa to prove to herself that he was wrong about her, indicating her dark nature can easily take over if the situation calls for it.
Kyōka's ability, Demon Snow (夜叉白雪, Yasha Shirayuki?), allows her to materialize a female 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 it does not comply to Kyōka's own wishes.
Though after joining the Armed Detective Agency 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.
- Acrobatics: Kyōka has shown immense physical capabilities, making superhuman leaps and slicing people with immense force, even without her ability.
- Sword Play: Kyōka is skilled with a sword.
According to Kōyō Ozaki, 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 in, and she served under Kōyō Ozaki as her protege. Shortly after joining the Mafia, she sought out Akutagawa Ryunosuke after hearing rumors that his Ability could cut through anything and begged him with desire in her eyes, to cut down Demon Snow to avenge her parents’ deaths and to then kill her. It was this encounter where Akutagawa found sympathy in Kyōka to give her a meaning to live by killing instead of wishing to die.
- The name Kyōka means "mirror, looking glass" (鏡) (kyō) and "flower, blossom" (花) (ka).
- Kyōka's surname Izumi means "spring, fountain" (泉).
- The real-life Kyōka Izumi was a man, whose real name was Kyōtarō Izumi (泉 鏡太郎).
- In reality, Kyōka was the protege of Kōyō Ozaki who admired the latter throughout his entire life, pursuing a career in literature due to Kōyō.
- Kyōka appears to have a photographic memory, often remembering people's faces and loads of information at a fast pace.
- Kyōka made an appearance in the mobile game "Kimito Lead Puzzle 18" as a stage boss and a limited-time character.
- Kyōka's teddy rabbit was won by Atsushi Nakajima on a claw machine.
- 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.