Since the Edo period of Japan, gladiator arenas have existed in various forms around the world. In these arenas, wealthy business owners and merchants hire gladiators to fight in unarmed combat where the winner takes all, called Kengan matches. Yamashita Kazuo, an average Japanese salaryman for Nogi Group witnesses a street fight in an alley between two mysterious fighters. One of the fighters, Tokita "Ashura" Ohma is scouted out by the Nogi Group CEO, Nogi Hideki, due to defeating their previous fighter in the street fight. Kazuo is roped into managing Ohma who joins these arenas only to devastate his opponents. His spectacular ability to crush his enemies catches the attention of big business owners, leading to his inclusion in the Kengan Annihilation Tournament under the invitation of Hideki. This tournament is held by the biggest CEOs in Japan and the winner gets the seat of Kengan Association chairman, a position which holds immense power and prestige. As the tournament unfolds Ohma tests his strength while struggling with his mysterious past coming back to haunt him as Kazuo struggles with managing Ohma and figuring out the true intentions as to why he was invited to this tournament.
