Two years after the events of Kengan Ashura, a young man named Narushima Koga aims to enter the Kengan matches, while also seeking out Tokita Ohma for a mysterious reason. He begins to work under Yamashita Kazuo when he meets Gaoh Ryuki, the spitting image of Ohma. Now with a massive showdown between the Kengan Association and Purgatory, another underground martial-arts fighting organization, looming in the background, how will Kouga become strong enough to take part in the legendary Kengan fights?

Since the Edo periods of Japan, gladiator arenas exist in certain areas. In these arenas, wealthy business owners and merchants hire gladiators to fight in unarmed combat where winner takes all. Tokita Ohma, nicknamed "Ashura", joins these arenas and devastates his opponents. His spectacular ability to crush his enemies catches the attention of the big business owners, including the Nogi Group chairman, Nogi Hideki.