In a re-imagined late 16th century Sengoku period Japan, warlord Isshin Ashina staged a bloody coup and seized control of the land of Ashina from the Interior Ministry. During this time, a nameless orphan is adopted by the wandering shinobi named Ukonzaemon Usui, known to many as Owl, who named the boy Wolf and trained him in the ways of the shinobi. Two decades later, the Ashina clan is on the brink of collapse due to a combination of the now elderly Isshin having fallen ill and the clan's enemies steadily closing in from all sides. Desperate to save his clan, Isshin's grandson Genichiro sought the Divine Heir Kuro so he can use the boy's "Dragon Heritage" to create an immortal army. Wolf, now a full fledged shinobi and Kuro's personal bodyguard, loses his left arm while failing to stop Genichiro. As he received the dragon’s blood from Kuro three years prior, Wolf survives his wounds and awakes in an abandoned temple. In the temple, he meets the Sculptor, a former shinobi named Sekijo who now carves Buddha statues, and Wolf finds that his missing arm has been replaced with the Shinobi Prosthetic, a sophisticated artificial arm that can wield a variety of gadgets and weaponry.