Biscuit Oliva, known as Mr. Unchained, migrated from Cuba to America. His frame towers with dense muscle, standing roughly 180 cm tall and weighing about 150 kg, sometimes appearing overweight when clothed. Brown skin, short black hair, and a thin black mustache define his appearance, often complemented by a smile during confrontations. In combat, he typically wears only a speedo to showcase his physique. Oliva serves as a highly compensated mercenary for the U.S. government, tackling threats beyond conventional law enforcement. His duties include acting as a specialized jailer at Arizona State Prison, maintaining order among dangerous inmates. In exchange for his services and residence at the prison, the government provides lavish accommodations: expansive living quarters, a personal library, and gourmet meals. This arrangement, stemming from an agreement where his luxury demands secured cooperation, grants him prison staff status with exceptional freedom. His background involves undisclosed criminal activities leading to incarceration. As a mercenary, he undertook missions for various governments, including an operation against a drug cartel where he encountered Yuujiro Hanma. Oliva killed the cartel leader but failed to engage Yuujiro in sustained combat after a surprise kick momentarily incapacitated him. Intellectually curious despite his physical dominance, Oliva maintains a vast personal library and studies subjects like toxicology and historical customs, demonstrating above-average cognitive abilities. However, his martial arts knowledge is less refined than Eastern masters like Doppo Orochi or Kaiou Kaku. He exhibits extreme arrogance and contempt towards opponents, resembling Yuujiro Hanma in demeanor but proving more cooperative with governments. He respects capable law enforcement figures like Morio Sonoda and martial artists who challenge him effectively. Oliva deeply cares for his girlfriend Maria, frequently visiting her despite her derisive attitude and physical condition, carrying her without hesitation. The title "Mr. Unchained" symbolizes his perceived freedom within the prison. Yet, this freedom is paradoxical; his attachment to luxury and status psychologically binds him. This vulnerability surfaces when Baki Hanma challenges his authority and mocks his "unchained" status, provoking visible rage. Later, Oliva urinates on Baki during a confinement visit to flaunt privileges, only to be further unsettled by Baki's dismissive reaction. Oliva's combat relies on brute strength and near-invulnerability. His extreme muscle density allows him to endure point-blank shotgun blasts, katana thrusts, and piercing attacks from fighters like Sikorsky. His endurance and pain tolerance are exceptional, absorbing devastating strikes with minimal injury. He trains by maintaining constant muscle tension, achieving feats like grounding helicopters bare-handed. He breaks spines with single moves, as seen against Kaiou You—whose body was likened to diamonds. His straightforward fighting style lacks technical complexity, leaving him vulnerable to intricate martial arts or unconventional tactics. Key engagements include reapprehending escaped death row convicts like Sikorsky and Doyle during the "Most Evil Death Row Convicts Saga," enduring attacks without significant injury. He participated in the "Great Chinese Tournament Saga" as Dorian’s manager, defeating Kaiou You and overcoming Shobun Ron’s "Hand Pocket" stance with forceful headbutts. Facing Baki Hanma in the "Great Prison Battle Saga" after Baki intentionally got arrested, Oliva defeated Jun Guevaru to retain his title but lost to Baki, who awakened a "Demon Face." Later, in "Baki-Dou," he battled the ancient sumo wrestler Nomi no Sukune II, suffering an initial defeat requiring rehabilitation before challenging Sukune to an informal rematch. A confrontation with Che Guevara caused global GPS disruptions due to intense seismic-like vibrations, though interpretations of this event vary. His character design draws inspiration from bodybuilder Sergio Oliva, a three-time Mr. Olympia.