Baki Hanma, once hailed as the 'World's Strongest Boy,' grows bored with his title and the ease of his victories after settling a long-standing conflict with his father. In the Kourakuen Underground Arena, he defends his reputation while battling ennui, effortlessly defeating challengers. Amidst this lull, a groundbreaking scientific experiment in Japan unveils the cloned samurai Musashi Miyamoto, who craves testing his mettle against Baki and Tokyo's elite fighters. However, Miyamoto's traditional values clash with the modern world's sensibilities, sparking conflicts as he challenges Baki's circle. As the legendary warrior strives to dominate this new era through combat, a clash with the vengeful Baki becomes inevitable, injecting thrill and tension into their confrontation.