Kanbei Shimada is a central figure and the de facto leader of the seven samurai assembled to defend the village of Kanna. He is an older, battle-hardened warrior whose past is defined by his service in a devastating conflict known as the Great War. Unlike many who might boast of their military history, Kanbei carries the weight of those battles without pride, as he was almost always on the losing side and witnessed the deaths of countless comrades. This history has deeply scarred him, leading him to live in the shadow of a painful and violent past. He often describes himself as a man whose heart has long since withered or dried up, a sentiment he expresses when declining a personal confession of love from the village priestess, Kirara. His demeanor is consistently calm, quiet, and wise, rarely displaying strong emotions. This stoic exterior is not coldness but rather the result of having seen too much suffering to be easily moved, making him a classic example of a knight in sour armor.

Kanbei is the first samurai recruited by Kirara, but his decision to accept the mission is not made lightly. He agrees to defend Kanna in exchange for nothing more than meals of rice, demonstrating that his motivations are not material gain but a lingering sense of duty and a chance to fight for a just cause, even if his heart can no longer find joy in battle. Throughout the series, his primary role is that of the group's strategist and commander. He devises the tactical plans to repel the bandits known as Nobuseri and the forces of the capital, often collaborating closely with his oldest friend and trusted partner, Shichiroji. His ability to command respect is natural, and the other samurai instinctively look to him for guidance, recognizing his superior wisdom and skill. He is a man of his word, demonstrated by his commitment to rescue Rikichi’s wife, Sanae, after promising to do so, pursuing her all the way to the capital.

Kanbei’s most significant relationships reveal different facets of his character. His bond with Shichiroji is the deepest, forged on the battlefields of the Great War. The two fought side-by-side, and their partnership remains seamless, marked by an unspoken understanding and complete trust. His relationship with the young, idealistic samurai Katsushiro Okamoto is more complex. Initially, Kanbei does not recognize the inexperienced youth as a true samurai, viewing him as naive. However, over the course of their battles, he observes Katsushiro’s growth, courage, and commitment. In a final act of acknowledgment, Kanbei passes his own sword to Katsushiro, signifying that he has become a worthy and successful samurai. He shares a quieter rivalry with the silent and deadly Kyuzo, a master duelist who joins the group specifically for a chance to fight Kanbei to the death. While Kyuzo views this as a primary motivation, Kanbei seems to regard it with less personal intensity. He also gradually accepts the boisterous and cyborg Kikuchiyo, another individual he initially dismissed, ultimately recognizing the farmer-turned-samurai as the seventh member of their band.

Throughout the story, Kanbei undergoes a subtle but meaningful development. He begins as a man resigned to his own emotional death, believing himself incapable of caring or feeling. Yet, his actions—fighting for the villagers, risking his life to save others, and ultimately investing in the future by training and honoring Katsushiro—contradict this self-assessment. While he still turns down Kirara’s romantic advance, stating there is no room for her in his dried-up heart, his final act of passing on his sword shows he has not completely withered. He has passed on his legacy, choosing to walk away from the village at the end with Shichiroji, his duty complete, leaving behind the next generation to carry on his ideals.

In terms of abilities, Kanbei is an exceptionally skilled swordsman, arguably the most formidable of the seven. His talent is so great that he can perform feats of incredible precision and strength, such as cutting through steel beams and giant mechanical foes with a single stroke of his chokutō sword. He is also capable of feats of unconventional defense, such as blocking a blade with his bare hands by gripping the flat of the sword. Beyond raw martial prowess, his greatest ability is his tactical genius and strategic mind. He is a master planner who can assess a battlefield, anticipate enemy movements, and organize a small force to achieve maximum effectiveness against overwhelming odds. While he prefers a fair fight when possible, he is a pragmatic warrior who does not hesitate to employ unconventional or seemingly underhanded tactics if the situation and the need to protect others demand it. Despite his incredible skill, the series emphasizes that he takes no pleasure in combat, viewing it as a grim necessity rather than a source of glory or satisfaction.