She was the unnamed mother of Kyōka Izumi.
Nothing is known much about her personality except that she valued and cherished her daughter, going as far as sacrificing herself in order to protect her.
She wielded the ability Demon Snow (夜叉白雪, Yasha Shirayuki?), which allowed her to materialize a female sword-wielding phantom known as Demon Snow. She was the original user of Demon Snow and transferred it to her daughter, Kyōka, before ordering Demon Snow to kill her due to an ability from an unknown person, which caused her to lose control over her body.
Together with her husband, she snuffed out countless lives upon orders of the government, having utilized her ability, Demon Snow. At some point, she gave Kyōka a mobile phone, which would eventually serve as Kyōka's memento of her mother.
One night three years ago, they were attacked by assassins at their house and were affected by a certain ability which used blood to control bodies. After her husband – who got affected by the blood-manipulating ability in the process – was slain by Demon Snow, she also got affected by the same ability. She then ordered Demon Snow to kill her in order to protect Kyōka and thereby transferred her ability to her daughter.
In the aftermath, the incident turned out to be a revenge plot against them by an unidentified ability user. Since the government could not reveal them to the public, their deaths were reported to be caused by an "ability gone out of control".
- Bungo Stray Dogs Manga: Chapter 43.