Kiwami Kimura is a central figure in the story of Ninja vs. Gokudo, a man whose life is a study in contradictions. He is introduced as a tall, suave, and charismatic elite salaryman in his late twenties, working as a planning director for the toy company Daiban. His outward appearance is that of a friendly and sociable office worker, a persona he maintains with practiced ease. However, this is a carefully constructed facade concealing his true identity as a high-ranking yakuza, serving as the shadow boss of the Second-Generation Takemoto-gumi. His body itself betrays this secret, with a large scar hidden beneath his hair and his torso completely covered in tattoos, the centerpiece of which is a depiction of Shiva, the Destroyer of Earth, an image that embodies his personal ideals.

The duality of his existence stems from a deep psychological wound. Due to a traumatic family environment and an accident that caused a head injury, Kiwami struggles to feel normal human emotions. He is unable to genuinely empathize with others, including his fellow yakuza, and he hides this void behind his affable, friendly mask. He understands concepts like sadness intellectually but cannot feel them, a condition that fosters a profound sense of isolation. This lack of emotion makes him a chillingly effective and charismatic villain, one who views the yakuza not simply as criminals, but as a refuge for society's outcasts and lonely individuals. His grand motivation is born from this perspective: he sincerely seeks to destroy the current society that excludes such "lonely individuals," vowing to overthrow the established order and the ninja who protect it using any means necessary, including short swords, guns, and drugs.

Within the story's central conflict, Kiwami serves as a primary antagonist and a major power broker. He is a founding member of a group called the Shattered Children and the financier behind Tickets to Hell, a dangerous paper drug that grants superhuman abilities. His actions are notable for their scale and ruthlessness. He orchestrated a ninja hunt in Akasaka, using dozens of yakuza as disposable pawns to lure out a high-ranking ninja, and after achieving a narrow, hard-fought victory, he desecrated the corpse to send a message. In response to the death of a close associate, he bombed the underground facilities of Kabukicho, causing a collapse that resulted in tens of thousands of civilian casualties. Despite this capacity for extreme violence and terror, he operates with a paradoxical code, showing genuine deference and respect to allies he deems visionary, while treating those he considers crude, such as his own subordinate Gamute, with cold disdain.

The most significant and transformative relationship in Kiwami's life is his unexpected friendship with Shinoha Tanaka, the very ninja sworn to destroy his kind. Their bond is forged through a shared, passionate love for the fictional Princess series of anime. It is through this connection that Kiwami, a man who believed he could no longer feel, begins to experience genuine human emotion. In the company of Shinoha, he finds himself laughing honestly and shedding tears, a development that reawakens a part of his humanity he thought was lost. He comes to deeply cherish Shinoha as his first and only true friend, even giving him a rare and powerful Ticket to Hell, saying he could use it if he were ever in danger. This friendship forms the emotional core of the narrative, a fragile and genuine connection built on a foundation of mutual deception, as neither initially knows the other's true identity as ninja and gokudo.

Other key relationships highlight different facets of his personality. His connection with his superior, Gamute, is described as a complex and troubled parent-child dynamic, which Kiwami treats as a strictly transactional master-disciple relationship. Unbeknownst to him, this very distortion is what begins to stir his dormant emotions of anger and sadness. His relationships with fellow yakuza leaders Kosei Yuzawa and Hiroki Yajima are markedly different; he respects their vision and mourns their deaths sincerely, carrying out massive acts of terrorism to honor their memories.

Throughout the series, Kiwami undergoes a subtle but significant development. While initially a near-emotionless master planner, his interactions with Shinoha force a change within him. Even after the truth of their identities is revealed, the memory of their genuine friendship lingers. Following the climactic revelation of Shinoha's identity, Kiwami resigns from his position at Daiban, his final act being a planning proposal for the next year's Princess series, and goes underground, initiating open hostilities against the ninja. The man who once sought to destroy the world for its outcasts is now forced to confront the one person who made him feel truly human.

In combat, Kiwami is exceptionally formidable. He employs an orthodox yakuza style, proficient with a handgun and a dagger, and is also skilled in Chinese martial arts. His true strength, however, lies in his charisma and tactical mind. He is a master manipulator who exploits his opponents' weaknesses in the heat of battle. His combat ability is said to surpass that of his superior, Gamute, and he is capable of defeating enhanced foes by precisely cutting their vital points. Although his own Gokudo Techniques remain largely unknown, he can imitate the techniques of his subordinates. He managed to defeat a powerful ninja in a direct confrontation, though he admitted it was a paper-thin victory that left him severely injured. Despite his immense power and cunning, Kiwami remains perpetually cautious and never arrogant, always aware of the terrifying potential of his ninja enemies.