Behind every major business deal in Japan is a fighter left lying on the ground... and another standing over the body. Ever since the Edo period, Japan's most influential companies have settled their conflicts through ruthless unarmed gladiator battles. In order to facilitate these matches, an underground organization, known as the Kengan Association, was created.

Ouma Tokita, a man nicknamed "The Ashura," strives to become the strongest martial artist. To do so, he becomes a Kengan fighter for a company called the Nogi Group. Shortly after, Kazou Yamashita, an employee with a stale job at the Nogi Group, is asked to become Ouma's manager. Now thrown into harrowing arenas, will this duo be able to survive in the brutal world of Kengan?