The mauling of a vicious, prehistoric-sized African elephant makes international headlines. Featured in reports of the aftermath, the sole survivor of one of the animal's rampages attributes its death to a lone, unarmed man—unknowingly describing Yuujirou Hanma, nicknamed the "Ogre" and often labeled as the "strongest creature on Earth." Elsewhere, Yuujirou's 18-year-old son Baki spars with an equally formidable beast: a praying mantis.

Content with his training and determined to overtake his father, Baki abducts American President George Bosch to begin his plans. This leads to his deliberate imprisonment at the infamous Arizona State Prison where Oliva Biscuit resides—the strongest man in the United States and an inmate allowed to leave of his own volition. Hoping to gauge his abilities, Baki challenges Oliva to a fight; but Oliva is preoccupied with his eccentric rival, Jun Guevaru. Known as the "Second," he is the only other prisoner to receive special treatment from the guards.

Bewildered yet intrigued, Baki learns about his fellow inmates and tolerates the hellish conditions of prison life while waiting for an opportunity to present itself.