Materia Black is one of the two Materia sisters, a pair of Frame Arms Girls built on the same base model. She is characterized by a mischievous and teasing personality, often displaying a slightly sadistic streak in contrast to her sister Materia White’s kind and innocent demeanor. Both sisters share the same minimalist body design, lacking heavy armor or weapons, which reflects their role as foundational or blank-slate units intended for customization and evolution. In the anime, Materia Black and her sister are introduced as challengers to the protagonist Gourai and her companions, proving to be formidable opponents even without additional equipment. After being defeated, they decide to stay with Ao Gennai and the other Frame Arms Girls. Materia Black’s motivations are primarily driven by a desire for playful conflict and close attachment to her sister, with whom she shares an affectionate and occasionally torturous bond. She demonstrates notable combat capability using only her base frame, emphasizing adaptability and raw potential. Over the course of the story, she shows openness to learning and forming relationships with the other characters, but her core personality remains consistently playful and teasing. Her appearance includes short blue hair and blue eyes, and she is often depicted wearing a black and silver external armored frame. As a Frame Arms Girl, her abilities can be expanded through the use of interchangeable parts and equipment, but she is most often seen fighting without such additions.