Shiro, a.k.a The Wretched Egg was adopted by Sorae Igarashi, for the purpose of replacing Sorae's newborn son, Ganta, to be a human experiment. After years of physiologic, and physical experimentation Shiro developed a superhuman power called ''Branch of Sin." This power requires that its user be lacerated or cut in some way, and the resulting bloodshed is then manipulated by psychokinesis.
As her powers developed her personality slowly broke into two parts, and soon she caused the Great Tokyo Earthquake, and became the source of the Deadman Virus, infecting other humans with their own Branches of Sin.
Sometime later, Shiro--as the Wretched Egg--escaped from confinement in the subterranean levels of Deadman Wonderland, where she was being confined. Locating
Ganta at his school, the Wretched Egg slaughtered her childhood friend's entire class, leaving only Ganta alive. He was held accountable for the deaths and sentenced to Deadman Wonderland.
The Wretched Egg either returned or was recaptured, so Shiro was on hand when Ganta arrived at the prison/amusement park. Befriending him, Shiro helped Ganta acclimate himself to life in Deadman Wonderland.
Unlike the other inmates at Deadman Wonderland, Shiro does not have an identification number in the prison's system mainframe, nor does she seem to require the antidote candy that the other inmates do to survive.
After having her two personalities combined, Shiro--feeling that she is beyond saving--asks Ganta, her current love interest, to kill her. He decides to comply, and the two engage in a fight to the death.
After over a decade of psychological torture, Shiro has developed a split personality. The two personalities are as so:
Shiro: A kind and playful girl, displaying the emotions of a child. Preadolescence is perhaps a time her personality retreats to, indicated by flashbacks to happy childhood memories with Ganta. Shiro is extremely concerned with Ganta's feelings regarding her.
The Wretched Egg: The Wretched Egg is a suicidal, homicidal creature who wants nothing more than death, destruction, and to die by Ganta's hands.
Shiro, being an albino has pale skin, pure white hair (that including eyelashes and eyebrows), and large red eyes. She has a rather slender and somewhat tall body marked with scars and stitches from her time as a human experiment. However, Shiro does not appear to have the extreme sensitivity to sunlight that most people afflicted with albinism suffer; this is perhaps a side effect of the experiments she underwent.
When the Shiro persona is dominant, she wears a skintight jumpsuit decorated with several red spirals resembling bulls-eyes, and a small neck brace. Whether the brace is necessary or just an odd fashion choice is unknown. The brace could be a collar, not dissimilar to those worn by the other inmates at Deadman Wonderland. When Shiro's personality is replaced by that of the Wretched Egg, her clothing is concealed by armor based on Aceman, a cartoon superhero from her shared childhood with Ganta.