Katakura Kojūrō from the anime Sengoku Basara - Samurai Kings is a character whose identity is deeply rooted in the historical legacy of the samurai Katakura Kagetsuna, a senior retainer of the Date clan during the late Sengoku period. In the series, he serves as the chief strategist and most trusted retainer to the young and impulsive warlord Date Masamune. So profound is his loyalty and tactical importance that he is famously known as the Right Eye of the Dragon, a title that reflects his role as the indispensable counterpart who sees what his one-eyed lord cannot.

Kojūrō's personality is defined by a calm, stern, and collected demeanor, a sharp contrast to Masamune's flamboyant and reckless nature. He is described as icy and stoic, always thinking several steps ahead on the battlefield and in political matters. This composed exterior, however, is a carefully maintained restraint over a much more volatile nature. In his youth, he was hot-headed and quick to anger, but he consciously subdued these traits to become the steady foundation for his lord, allowing Masamune to be the bold and ambitious leader. Behaving as a mentor-protector and a brotherly figure, he is unafraid to scold his master or even physically intervene, such as knocking Masamune unconscious to prevent him from fighting while injured.

His primary motivation is absolute and unwavering: to see Date Masamune succeed and fulfill his ambition of uniting Japan. This loyalty is not born of blind obedience but of a profound belief in Masamune's potential. He has dedicated his entire life to serving as the pillar supporting his lord's dream, managing clan affairs during Masamune's absences or injuries, and ensuring the clan's survival. This dedication is so complete that he has been willing to sacrifice his own life on multiple occasions, famously impersonating Masamune on the battlefield by shouting "I am Masamune!" to draw enemy fire away from his young lord, an act that nearly cost him his life. In one instance, he even attempted to commit seppuku to atone for a perceived failure in protecting Masamune.

In the story, Kojūrō acts as the tactical genius of the Date army, orchestrating defenses and devising strategies that allow Masamune's forces to overcome overwhelming odds. His role is that of the stabilizing anchor, providing pragmatic guidance and cautionary advice. During the Toyotomi campaign, it is Kojūrō who politically advises Masamune to surrender to Toyotomi Hideyoshi, a difficult but necessary choice to preserve the Date clan's future. His strategic insight is often the decisive factor in battle, allowing him to outmaneuver other brilliant minds, such as when he quickly dismantled a complex trap set by the strategist Takenaka Hanbei.

Kojūrō's key relationships center on his bond with Masamune, which is one of near-absolute trust forged over a lifetime. He is more than a retainer; he is the one person who raised and watched over the young lord from childhood, making their connection deeply personal. When not fighting, he often performs humble tasks like cooking for Masamune and tending to a personal garden, showcasing a rare, gentle side reserved for his lord. While his primary interactions are with his master, he also has notable antagonistic relationships with figures like Matsunaga Hisahide and Takenaka Hanbei, against whom his protective fury is unleashed when they threaten Masamune.

The development of Katakura Kojūrō is largely a revelation of his hidden depths. While he appears as a perfect and unwavering retainer, his story arc explores the internal struggle of maintaining such a composed facade. It is revealed that his calm nature is a choice, a restraint he practices to balance his master's recklessness. In moments of extreme provocation, such as when Masamune is attacked dishonorably, this restraint shatters, revealing the ruthless and far more aggressive warrior beneath, a side that even his enemies fear. This hidden intensity is so pronounced that the oath inscribed on his blade is described as a seal on his inner darkness.

In terms of notable abilities, Kojūrō is an exceptionally skilled swordsman, typically wielding a daisho, the paired long and short swords of the samurai. Although his fighting style is straightforward and powerful, lacking the flashy acrobatics of other characters, he is repeatedly hinted to be potentially stronger than even Masamune himself. Like his lord, his elemental affinity is lightning, which manifests as an electrical aura around his blade, though he normally restrains this power, only unleashing it when his intense anger is triggered. Beyond martial prowess, his true strength lies in his brilliant strategic mind and political acumen, making him indispensable to Masamune's campaigns and the governance of their territory. His practical skills extend to mundane life as well, as he is portrayed as a capable farmer, gardener, and cook.