Byakki is a White Oni (the only one of her kind). Unlike other Oni, she doesn't have any horns, and her entire appearance is white. Her skin and hair are both naturally white, and she only wears white (though she isn't seen dressed in anything but wraps that seal her powers most of the time). The other non-white she has is in her eyes which are a deep red. Byakki is quite unique in her powers for she is extremely powerful and agile, to the point of being nearly unbeatable by many beings. In contrast, she has virtually no defensive capabilities, meaning that if she gets injured it could easily defeat her.

Along with her amazing offensive abilities, she feeds off of the forces of other beings, absorbing from them with no more than a momentary contact with her hand or even her clothing; the amount she drains varies, usually just leaving the being affected weakened but can cause them to collapse for several days if she takes a large amount; this can obviously be used in combat to easily defeat nearly any opponent, though it will obviously fail if her opponent has nothing to absorbed. She was given the name Shiro by Tōru when he first met her, since no one there knew her real name.

(Source: Wikipedia)