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.

After retiring from public fighting and getting fired from underground fighting, 27 year old Tenma Nozomi's zest for life is gradually dwindling away. It's hard to be at the bottom with nowhere to go, and that's exactly where she and her two friends are. However, Nozomi hits upon an idea that may just solve all of their problems: they could make their own underground fighting circuit for women, and tap into an underexplored market. As good as that sounds, her insistence on including the unknown quantity Hongou Hina may prove to be more than she bargained for...