"To stay silent and do what you're told is a cowardly decision," Junk Dog, an underground fighter of Megalo Box, an advancement of boxing that uses mechanical limbs known as Gear to increase the speed and strength of its practitioners, says. Despite the young man's obvious talent as a boxer, the illegality of his involvement requires him to make a living by throwing bouts as directed by his boss Gansaku Nanbu. This all changes when Yuuri, the Megalo Box champion, enters his dingy ring disguised as just another contender. Junk Dog, who was knocked out in a single round, issues a challenge: "If you're serious about fighting me again, battle your way up to me."