After numerous deadly fights against strong opponents, Baki has finally reached the level to challenge his father Yuujirou, The Strongest Creature on Earth. Before his fight against Yuujirou, Baki chooses the "just right" sparring opponent in Mr. Unchained, a.k.a. Biscuit Oliva, who is considered to be as strong as Yuujirou. Baki intends to become one step stronger by defeating Oliva. However, Oliva is now at the "Black Pentagon": the prison complex in Arizona, USA exclusively used to contain extremely dangerous criminals. In order to fight Oliva, Baki decides to be imprisoned at the Black Pentagon, but other extraordinary fighters are waiting for him. The only rule in this prison is power!! Source: Official website