"Kengan Ashura" is set in a world where powerful corporations and wealthy individuals settle disputes through gladiatorial combat, employing fighters known as "Kengan" fighters to represent their interests. The story centers on Tokita Ohma, a skilled and enigmatic martial artist who becomes a Kengan fighter under the employ of the Nogi Group, a prominent corporation. Ohma’s raw talent and unorthodox fighting style quickly draw attention in the brutal underground arena, where fighters battle to the death or near-death using a variety of martial arts, weapons, and unique techniques.

The narrative unfolds through a series of high-stakes tournaments, culminating in the Kengan Annihilation Tournament, where the most powerful fighters and their corporate sponsors compete for dominance. Ohma’s journey is driven by his quest to uncover his mysterious past and the origins of his martial arts style, the Niko Style. Along the way, he encounters a diverse cast of fighters, each with their own motivations, backstories, and fighting philosophies. Key characters include Kazuo Yamashita, a middle-aged salaryman who becomes Ohma’s handler and develops a paternal bond with him, and fighters like Gaolang Wongsawat, a master boxer, and Raian Kure, a ruthless member of the Kure Clan, known for their deadly assassination techniques.

The series explores themes of power, ambition, and the moral complexities of corporate warfare, as the fighters’ personal struggles intersect with the larger machinations of their sponsors. The battles are intense and meticulously choreographed, showcasing a wide range of martial arts styles and strategies. As the tournament progresses, alliances shift, rivalries deepen, and the true nature of the Kengan matches is revealed, exposing the darker undercurrents of the corporate world and the sacrifices made in the pursuit of victory. The story balances action with character development, providing insight into the fighters’ lives and the stakes they face both inside and outside the arena.