Biko "B-ko" Daitokuji is the heiress of the powerful Daitokuji Financial Group, a supplier of advanced robotic weapons systems to global defense forces. In the original film continuity, she is a wealthy, academically gifted student at Graviton High School, recognized for her arrogance and technological brilliance. She harbors an obsessive rivalry with classmate A-ko Magami, stemming from childhood incidents where B-ko bullied C-ko Kotobuki only to be thwarted by A-ko, leading to an unresolved confrontation. As teenagers, B-ko renews her fixation on C-ko and designs increasingly sophisticated mecha—including the Daitokuji Power Suit, Max 5000, Abachiyama 5, Queen Margarita, and Robo A-ko 839—to eliminate A-ko. Her primary weapon is the Akagiyama-23 battlesuit, a revealing purple armor granting superhuman strength, speed, flight capabilities, wrist-mounted missiles, and an energy whip, which she often deploys beneath her regular clothing for instant access. She commands subordinates Mari (a muscular enigma), Asa (a manipulative spy), Uma (a pessimistic analyst), and Ine (a skilled cameraperson) to pilot her mecha or conduct reconnaissance. Despite her resources, B-ko's schemes consistently fail against A-ko's innate powers, escalating her temper and vindictiveness. Her motivations blend a desire to control C-ko with deep-seated insecurity and ego, often manifesting as megalomaniacal rants. In the film sequels, her obsession extends to competing with A-ko for the affection of motorcyclist Kei, who only pursues C-ko. This rivalry culminates in citywide destruction, prompting military evacuation orders during their fights.

In the alternate continuity of *Uncivil Wars* (also titled *A-ko the Versus*), B-ko is a 21-year-old bounty hunter partnered with A-ko on a desert planet, scavenging giant sand turtles for income. Their dynamic shifts from enemies to vitriolic allies, with B-ko displaying no romantic interest in C-ko. C-ko—now the daughter of a galactic corporate executive—accidentally crashes into their lives after being kidnapped by space pirates Grash and Raiza. When the pirates abduct C-ko again, B-ko and A-ko ally with galactic policeman Maruten to rescue her, confronting pirate leader Gail (whom B-ko finds attractive) and thwarting the cultist Xena's multiverse-merging scheme. B-ko's technological prowess remains central; she leverages her intellect to navigate crises, though profit motives often drive her actions. After returning C-ko and saving the multiverse, she and A-ko pursue Maruten for claiming credit, leaving their partnership ambiguously adversarial. This continuity highlights her adaptability and pragmatic ruthlessness, contrasting with the school-based obsessions of the original films. Across all media, B-ko's character combines intellectual superiority, technological innovation, and a volatile personality driven by rivalry, ego, and shifting alliances.