Born at Ueno Castle in the Valley of Broken Spirits in Aileron, Shizuka is a descendant of Hanzo Hattori of the Hattori Clan, daughter of Teresa and Keiji Hattori, younger sister of Ryushi Hattori, niece of Kenji Hattori, cousin of Kenshin Hattori and granddaughter of Ryuji and Yukie Hattori. Her mother died when she was very young and she unfortunately does not have many memories of her. Since then, she was largely raised by her brother. Because of the large number of enemies her family has as a result of an ancient conflict, Shizuka has been targeted by their enemies since she was a child. One such assassination attempt resulted in the death of her older brother, which she never truly got over. Because of this, Shizuka has been trained since she was young to be a ruthless, deadly and effective fighter.
Following her brother's death, she was chosen over her cousin by their grandfather to be the next family head and his successor, inheriting the position from her brother. As a member of the Hattori Clan, she takes part in various missions of their mercenary group, the Masanari Black Flowers, which she would also eventually inherit leadership over. She thorough researches her clients and potential victims to make sure the jobs are not morally wrong and that there are no innocent or civilian causalities.
As a result of both her brother's death and the constant danger in her life, Shizuka hardened herself emotionally in order to both keep herself from feeling pain and vulnerability again and to make sure she always keeps a level head by not letting anything affect her or compromise her judgement or ability.
While searching for her brother's killer, Shizuka trains with Azreal to master his powers, which, unlike others partnered with guardian spirits, she can access even when Azreal is absent. At some point in her travels, she found herself crossing paths with a young man named Ryan Murphy. Ryan took an interest in her and, out of curiosity, followed her while she was on a mission. Shizuka became irritated with this and threatened him with hostility and violence to stay out of her business. However, when one of her family's enemies spotted them together, she was forced to take Ryan into protective custody, as he was now believed to be associated with her.