Four friends bound by destiny and unbeatable in the dark world. When a casino attack goes wrong as a result of betrayal, fate turns them into enemies. Now, forced to aim the gun at each other's hearts, their unavoidable battle begins.

Fuma ninja clan is a secret ninja tribe that is waiting for the "Orochi" (gigantic snake) to resurrect for generations. Shirasu and his twin brother Ichiu grew up in this viscous environment and this tells how they become the leaders of the clan.