This serie is a prequel of Kengan Asura series.

After the ninja abolition act was passed in Japan, ninjas were forced to relocate. How will 15 year-old Shinoko handle transferring to an American high school, when she can barely speak English and is still a ninja in training!?

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. Toki Taouma, 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.