|Family|| Ganta Igarashi (Son)|
Shiro (Adopted Daughter)
|Affiliations||National Medical and Health Center|
|Manga debut||Chapter 1|
|Anime debut||Episode 5|
Sorae Igarashi was the mother of Ganta Igarashi. She was a doctor and was involved in the development of the Wretched Egg as well as the Mother Goose System. She died by committing suicide. Sorae couldn't bear the guilt of turning Shiro into a monster. In the anime, Ganta explains that ten years before being imprisoned in Deadman Wonderland, his mother had died.
Over fifteen years before the main story, Sorae Igarashi worked as a professor for the Medical Center in Tokyo alongside fellow scientist Hagire Rinichirō. The team participated in a variety of research ventures on the human body, and subjecting both living and dead to immoral experiments. When confronted with the need of a living subject for their next experiment, Sorae recommended her own unborn child as the next scientific commodity, her level of callousness even surprising the equally cold-hearted Hagire. This changed when Ganta was born. As her maternal instincts quickly surfaced, she unexpectedly developed an attachment to her son and could not bring herself to involve him in her experiments. Sorae went on to obtain another baby to replace Ganta in her research. She adopted an orphaned albino infant and brought the baby to the laboratory. Hagire notices the hair color and immediately figures out that the new child is not Ganta. But Sorae tearfully refused to give up her child and presented the albino child to use for the experiments instead. The white-haired child is later given the name Shiro.
Sorae lived together with Ganta and Shiro at the medical institution where she and her team conducted research to heighten a human's immune abilities, their "guinea pig" for this research being Shiro. Over the years she developed a bond with the young albino girl, treating her as a daughter and giving her presents and treats while not performing experiments. When Shiro became irritated playing with Ganta due to his weakness, Sorae was forced to remind Shiro of her enhanced strength and endurance. Although her emotional attachment to the albino girl caused Sorae to despise her team's experiments, she continued working alongside Hagire. Hagire became sickly interested in Shiro and prompted Sorae to continue with their endeavors. Due to the inhumane and brutal experiments performed on Shiro, the albino girl's mind developed a second personality to deal with the pain. The research ultimately gave birth to the Wretched Egg.
Following the awakening of Shiro's destructive personality, Ganta's mother composed a lullaby capable of suppressing the evil within her. She would often play this song on the piano for Ganta and Shiro with tears in her eyes, knowing the true purpose of the melody and what must eventually be done. At the time Sorae was completely destroyed knowing what she had done to Shiro. She often cried and played her piano singing different versions of the lullaby. When The Wretched Egg could no longer bear the pain and caused the Great Tokyo Earthquake, Sorae sent Ganta to live with his father, knowing that Shiro's suffering was her responsibility. Having removed Shiro from Ganta's memories, he does not recognize the name of his friend when mentioned by his mother. Knowing that he would be better off not knowing, she simply tells him to take care.
The Great Tokyo Earthquake was brought about when Shiro learned from Sorae Igarashi that if she used too much of her power she could kill herself. Wishing death sooner than the suffering she was being subjected to, she unleashed a large amount of her power in an attempt to kill herself. While doing this, she intentionally spared Sorae Igarashi, as she was one of the only consolations she had.
Hoping to lock away the alternate personality forever, Sorae created the Mother Goose System, an invention that constantly emanated the lullaby in order to keep Shiro from succumbing to the Wretched Egg's influence. She then sealed the machine to prevent anyone from tampering with it, leaving behind a hidden journal explaining how to operate the device. An injured Hagire later confronts Sorae about releasing the Wretched Egg after the earthquake, but she refuses to give him that information. Sorae then pulls a gun from her lab coat and kills herself.
Sorae has long black hair that is kept in a braid over her right shoulder. She wears regular clothes; a green sweater and light pants. Over her clothes, she wears a white lab coat. She is always seen walking with sandals on.
Around the time she was pregnant, she had kept her hair kept cut to neck length.
Sorae was initially a harsh individual, as noticed by Hagire Rinichirō in their days working together at the institution. She was willing to do anything for the purpose of science and reacted coldly towards her research subjects, even giving birth to Ganta for the sole purpose of using him as the subject for her experimentation. Her personality changed after the birth of her son. Overcome by motherly instinct, she could no longer stand the thought of using him as a guinea pig and quickly sought another infant to use as a substitute.
Despite having intended to experiment on them both, Sorae seemed to be a loving and caring mother to Ganta and Shiro, having lost the heart to experiment on her own child, while despising herself for the things she and Hagire did to Shiro in the name of research. While outside of the lab, she treated her like her own daughter and gave her presents and treats just like she did with Ganta, and often cried to herself when forced to carry out the experiments. As a last glimmer of hope to save Shiro, she created the Mother Goose System along with the lullaby that would seal away the destructive powers of the Wretched Egg.
Sorae was a scientist working with Hagire and when they came upon Shiro (A.K.A the Wretched Egg) Hagire became sickly interested in Shiro and performed gruesome "experiments" on her when Shiro couldn't handle the pain and formed another personality. At the time Sorae was completely destroyed knowing what she had done to Shiro. She often cried and played her piano singing different versions of the Lullaby. When The Wretched Egg could no longer bear the pain and caused the great earthquake she sent Ganta away to his father saying " I can't run away... That child... I can't leave Shiro like that."  Ganta removing Shiro from his memories questions who is that and she tells him to take care. For the time being that is the last time we ever heard of Sorae. It is later revealed that Hagire confronted Sorae after the Earthquake, at which time she committed suicide.