Ange Ushiromiya, daughter of Rudolf and Kyrie Ushiromiya, is Battler Ushiromiya's half-sister through Rudolf's previous marriage to Asumu. Born as Rudolf's illegitimate child with Kyrie, she enjoyed a relatively happy early childhood despite limited contact with the brother she deeply admired. A cherished memory from her youth was Battler gifting her cheap hair ornaments won from a crane game; she treasured them throughout her life. She also shared a close bond with her cousin Maria Ushiromiya, often playing with Maria's doll Sakutarou during family gatherings.

Her life shattered in October 1986 when, aged six, illness prevented her from attending the Ushiromiya family conference on Rokkenjima. During the Rokkenjima Massacre, all family members except her aunt Eva Ushiromiya perished. Eva became Ange's legal guardian, but their relationship deteriorated under Eva's harsh treatment and Bernkastel's manipulation. The witch Bernkastel exploited Ange's grief, convincing her to reject Eva's maternal overtures with the false promise that doing so would reunite her with her deceased family. This left Ange isolated and embittered.

As a teenager at St. Lucia Academy, Ange faced severe bullying. Classmates accused her family of orchestrating the massacre for inheritance, fueled by public knowledge of her parents' fraudulent business dealings and her direct blood relation to Battler. Lonely and traumatized, she found solace in Maria's diary, which taught her magic. She created imaginary companions, including manifestations of the Seven Stakes of Purgatory and Sakutarou. Consumed by despair, she ordered these entities to kill her tormentors. When they refused, she denied their existence, causing them to vanish—including her closest friend, Mammon, who noted Ange's profound loneliness before disappearing.

After Eva's death in 1998, Ange inherited the Ushiromiya fortune and title of family head. On Eva's deathbed, she refused to reveal the truth of Rokkenjima, telling Ange to "ask her parents in hell." This rejection spurred Ange's quest for answers. She inherited the mantle of the Golden Witch Beatrice from Eva, becoming known as ANGE-Beatrice, the Witch of Resurrection and the Endless Witch. Her existence twelve years after the massacre granted her unique magical resistance, rendering her immune to Beatrice's magic and enabling her to counteract supernatural forces. Her abilities included Endless Magic, restoring objects or beings to their original state, and Resurrection Magic, reviving entities whose existence had been denied—such as Sakutarou, whom Beatrice could not resurrect after Rosa's rejection.

Ange's magical prowess manifested in conceptual weapons called Truths. The Blue Truth functioned as a theoretical counterargument, often taking physical form as stakes. The Red Truth stated irrefutable facts. Her unique Golden Truth could override even the Red Truth, exemplified when she used it to protect her family from Bernkastel's attacks. Her ultimate ability, the Golden Eagle, overpowered Bernkastel and fractured the metaphysical City of Books.

Her personality evolved from a cheerful child to a cold, cynical teenager marked by sarcasm and the recurring phrase "It's useless, it's all useless." Despite her hardened exterior, she remained emotionally vulnerable, particularly regarding Battler and the hair ornaments he gave her. Her journey culminated in Twilight of the Golden Witch, where she achieved full mastery of her powers. She resurrected her family within the "cat box" of infinite possibilities and accepted the truth of Rokkenjima. This acceptance symbolized her transition from seeking vengeance to embracing hope, resolving to live on despite her losses.