Kagemaru was the double of Tokugawa Shige Shige.
Background[]
Since childhood, he has been the double of Shigeshige. He looks exactly like Shigeshige, to the point where he got kidnapped because they mistook him as Shigeshige.
This results Shigeshige to secretly leave the palace at night with his Oniwaban friends to go rescue him. Shigeshige ends up getting injured while protecting him. Shigeshige asks him to pretend to be the shogun for the next 6 months.
Appearance[]
He looks exactly like Shigeshige except he doesn't have a scar on his chest, which Shigeshige gets from protecting him.
Story[]
Shogun Assassination Arc[]
A plan was made to use doubles to diverse the enemy after it was revealed the Shogun's cup was poisoned. Hattori Zenzou doesn't listen to this plan and actually secretly switches the Shogun out for Kagemaru.
He ends up sacrificing his life for the Shogun. Beforehand, Hattori and him discuss if he is fully prepared to die, he replies with "I, Kagemaru, wouldn't be here if he hadn't saved my life back then. Use it for his sake." later on Hattori slices his head off, making it appear as if the Shogun had died.
This makes everyone believe the Shogun is dead when really the Shogun is hiding undercover among the Iga Clan.