However, in the book "The Maker of Modern Japan" it describes an incident about Kanetsugu as just that, a brutal Uesugi samurai willing to do anything for his lord and the Uesugi clan. After the death of Toyotomi Hideyoshi but prior to the defining battle of Sekigahara in 1600, Tokugawa Ieyasu learned that his rival Uesugi Kagekatsu was busy building a new castle at Kazashigahara. Ieyasu questioned Kagekatsu but received only a response from Kagekatsu's chief retainer Naoe Kanetsugu. Kanetsugu simply replied that these were normal repairs and nothing more. In response, Ieyasu sent an envoy to persuade Uesugi to visit him, but Naoe regarded the envoy as a spy, and recommended Uesugi to have him put to death. But the envoy somehow got wind of this and made his escape. This incident was one of the events that led to the final defining battle for power in Japan, Sekigahara, which led to Ieyasu becoming the supreme ruler, the Shogun.
The book reveals more about Ieyasu's style and about Naoe Kanestugu following Sekigahara. Ieyasu considered it politic not to be too drastic in his penalties to those who fought against him at Sekigahara. This is revealed in his reply to his chief retainer Honda Masanobu's suggestion that Naoe Kanetsugu deserved to be punished (death), since he had been one of the chief instigators of the rebellion. "No doubt," replied Ieyasu, "and not only he, but the chief councillors of Mori and Shimazu and the others, because they all pushed their lords at Ishida's instigation (Ishida Mitsunari). And if I punish Naoe the others will get upset and run away to their provinces, and we may have all the trouble over again."
The real Naoe Kanetsugu, at least the one portrayed in the book, does not really match the one in the NHK drama Tenchijin. My feeling is the book portrays him a little more accurately. None the less, the drama Tenchijin is one of my favorite Taiga dramas I have seen. I think the characters for Oda Nobunaga, Tokugawa Ieyasu, Toyotomi Hideyoshi and Uesugi Kagekatsu are really good. I am interested to see how Tenchijin shows how Naoe 'instigates' the rebellion of Sekigahara.