Lord Tokugawa Tsunatoyo, bound for Edo to be sworn in as the next shogun, is the target of merciless ninja assassins hired by corrupt officials hoping to put their own candidate in his place. His only hope is the “Oniwaban,” the shogunate’s secret ninja force, sworn to throw their lives down recklessly to prevent this coup. But will they stand a chance of getting the lord to his ceremony in time? A perilous chase, betrayal after betrayal, and a final bloodbath await them as ninja battle ninja in one last, desperate struggle.

Deep in the mountains of feudal Japan, a group of children endure cruel and unorthodox training in order to become the Shogunate's most secret and deadly weapons - the Demon Spies! Their true identities are hidden - even from each other. Behind their demon masks, they are educated in the deadly arts of infiltration, espionage, assassination - and seduction! If they survive to become strong enough to kill their teachers, they will become - the Demon Spies! Sent on a suicide mission to uncover a deadly conspiracy, five inexperienced Demon Spies must infiltrate a powerful fief, discover the location of its secret arsenal, and destroy it. But Lord Shogen, the Demon Hunter, plans to brutally interrogate, ingeniously torture, and cruelly execute - the Demon Spies!

Mendou hires a new personal Ninja with some very unusual abilities, only to have him fall head-over-heels for his manipulative sister, Ryoko.