From the top of Megacity S1-9, the Sovereign Khan rules with fists of iron and flesh. Beneath the city s rotting foundations , a vengeful warrior embarks on a journey to murder him . 5 years prior to the events of Slave Zero , Slave Zero X brings new life to a world where horrific , living machines known as Slaves are primed to become the latest tools of war in humanity s long and bloody history . A secret band of warriors known as The Guardians hope to stop these biomecha from being unleashed upon the world, but one swordsman among their ranks has a different idea: use the enemys own weapon against them. By merging with a stolen Slave Unit Prototype, Shou will become a furious Devil in pursuit of killing a false God.