Right after winning the Champion Carnival, Ryuuji Takane faced a challenge from the U.S. Junior Champion, Black Shaft. As the World Tournament approached, Ryuuji, Takeshi Kawai, Kazuki Shinatora, Ishimatsu Katori, and Jun Kenzaki had to prove their prowess as world-class boxers, not just to Shaft but to the entire world. However, Shaft did not recruit fellow boxers for his challenge. Instead, he gathered a convicted criminal from Death Row, the leader of an American gang known as the Great Angels, a mysterious woman, and the "Dark Emperor of the South". In addition, Shaft negotiated with Don Juliano, the Italian Junior Champion, just in case...