Junk Dog, an underground fighter with the alias of "Gearless Joe" sets out to join the worlds most prestigious mecha boxing championship, Megalonia.
A desolate land stretches out from the city of poverty. A motorcycle speeds recklessly, blowing clouds of sand and dust. The rider is the protagonist of this story – he has neither a name nor a past. All he has is his ring name, “Junk Dog” and a technique for rigging MEGALOBOX matches with his pal Gansaku Nanbu, which they use to support their hand-to-mouth lives. JD is bored, resigned, and unfulfilled. Yuri has been the reigning champion of MEGALOBOX for the past few years. He has the skills and presence of a true champion. This is a story of JD and his rival, Yuri.

สร้างขึ้นเพื่อฉลองครบรอบ 50 ปีของมังงะ "โจ สิงห์สังเวียน" มนุษย์เครื่องจักรนักสู้ที่รู้จักกันในนาม "นักชกเดือดสังเวียนมืด" จะมาเปิดศึกชิงความสุดยอดแห่งการชกมวย