The “Seven Deadly Sins”—a group of evil knights who conspired to overthrow the kingdom of Britannia—were said to have been eradicated by the Holy Knights, although some claim that they still live. Ten years later, the Holy Knights have staged a Coup d'état and assassinated the king, becoming the new, tyrannical rulers of the kingdom. Elizabeth, the king's only daughter, sets out on a journey to find the “Seven Deadly Sins,” and to enlist their help in taking back the kingdom.

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.