"That's the coward's way out - to simply remain silent and obey orders." These were the words spoken by Junk Dog, a participant in Megalo Box, a form of boxing that employs mechanical limbs called Gear to enhance its users' speed and strength. Despite his impressive boxing abilities, Junk Dog is forced to throw matches due to the illegal nature of his participation and the demands of his boss, Gansaku Nanbu. However, everything changes when a renowned fighter named Yuuri challenges him to rise up the ranks and battle him again. Inspired and aided by the criminal syndicate that orchestrated his thrown matches, Junk Dog - now known as "Joe" - enters Megalonia, a tournament that will determine the strongest Megalo Boxer. With just three months to qualify, Joe starts at the very bottom of the fighter list, prepared to face off against a variety of formidable opponents on his way to facing his rival once again.