UB (Underground Brawl) is an ultimate fighting tournament that doesn't follow the standard rules of the official sport, UFC (Ultimate Fighting Championship). Consequently, this tournament is hidden from the public and has become a playground for the upper class. But one man is destined to end the cruel government's uprise. That man is Jack Knife.

The story will mostly focus on Jack's fighting encounters in the UB tournament and how he will recover his forgotten past.