Historically: Fourth son of the noted warrior Nagao Tamekage, Kenshin wrested control of the Nagao clan from his brother Nagao Harukage and fought for control of Echigo Province. He accepted the name Uesugi Masatora when he gave refuge to his nominal lord, Uesugi Norimasa, and at his urging campaigned to push the Houjou out of the Kantou Region.
He adopted the name "Kenshin" when he became a Buddhist monk and a devotee of Bishamonten. The standard his army carried onto the battlefield bore the character 毘 ("bi") for Eight-Sword Bishamonten. He battled Takeda Shingen five times at Kawanakajima, as well as the Houjou and Ashina clans and Oda Nobunaga, whom he defeated despited being outnumbered. However, Kenshin died soon after the battle. He named his two adopted sons, Uesugi Kagetora and Uesugi Kagekatsu, his heirs, hoping that they would divide the Uesugi lands peacefully between them after his death.
In Mirage of Blaze: He became a god of war after his death, ascending from Nin Dou to Ten Dou, and established the Meikai Uesugi Army to ensure that the peace of Japan is not disrupted by the onshou. He named Kagetora as its commander.