Asagi Aiba is a high school student at Saikai Academy and a classmate of Kojou Akatsuki, living on Itogami Island. She has strawberry blonde hair, which she dyed from its natural black, typically styled in a long ponytail secured with a pink ribbon, and pinkish-red eyes. Her physical measurements are B83, W57, H82. During middle school, her appearance was different, including black hair and non-prescription glasses. Her personality shifted significantly in middle school, transforming from a sensible, mature girl into a more flippant, flirtatious, and stylish individual, a change directly stemming from meeting Kojou and developing strong romantic feelings for him. She often displays a tsundere-like attitude toward Kojou, prone to jealousy, especially concerning Yukina Himeragi, though a hidden solemn and deductive side emerges during grave situations. Asagi works part-time for the Itogami Island Management Corporation as an expert programmer and hacker, operating under the online alias "Cyber Empress." Her hacking abilities, aided by an artificial intelligence program named Mogwai, intensify with a red glow around her eyes and dramatically accelerated finger movements, allowing her to decipher complex codes, hack entire corporations, and fend off coordinated cyber attacks. She was once coerced into activating the ancient weapon Nalakuvera but later devised a countermeasure to stop it. Crucially, she holds the hidden identity of the Priestess of Cain, granting her practical immortality while on Itogami Island, which functions as Cain's altar. Her programming prowess and connection to Mogwai are linked to this heritage. Asagi has harbored romantic feelings for Kojou since their middle school days, considering him her best friend alongside Motoki Yaze, who is aware of her feelings. She later marries Kojou, and they have a daughter named Moegi Akatsuki. Her family background includes the loss of her biological mother, leading to a strained relationship with her stepmother. At one point, her body is temporarily possessed by an entity named Nina during a crisis. Throughout the series, she consistently uses her intellect and skills to support Kojou and protect Itogami Island.