นักชกมวย JD (Junk Dog) ที่ได้มาชกในสังเวียนมืดใต้ดิน และเดิมพันทุกสิ่งในการชกด้วยสิ่งที่เรียกว่าชะตากรรม โปรเจคออริจินัลทีวีอนิเมะ ฉลองครบรอบ 50 ปีของมังงะ Ashita no Joe โจ สิงห์สังเวียน
"To clam up and do as you are told, that is the fainthearted selection." These ar the words of Junk Dog, associate degree underground fighter of Megalo Box, associate degree evolution of boxing that utilizes mechanical limbs called Gear to reinforce the speed and power of its users. Despite the young man's brimful potential as a boxer, the embezzled nature of his participation forces him to create a living off of throwing matches as settled by his boss Gansaku Nanbu. However, this all changes once the Megalo Box champion Yuuri enters his shabby ring below the colour of simply another competitor. Taken come in one spherical, Junk Dog is left with a challenge: "If you are serious concerning fighting ME once more, then fight your far to ME and my ring."
Filled with overwhelming excitement and backed by the criminal syndicate answerable for his thrown matches, Junk Dog enters Megalonia: a world-spanning tournament which will decide the strongest Megalo Boxer of all of them. Having no name of his own, he takes on the cognomen of "Joe" as he begins his climb from the terribly bottom of the stratified list of fighters. With solely 3 months left to qualify, Joe should bully off against opponents the likes of that he has ne'er fought so as to fulfill the challenge of his rival.