Kin'emon, also known by his epithet "Foxfire" Kin'emon, is a samurai from the region of Kuri in the isolated Land of Wano. Born fifty-six years before the present storyline, he is a man who has lived through extraordinary circumstances. In his youth, Kin'emon was not a noble warrior but rather an infamous thug, gambler, and thief who often stole from his childhood friend, Tsuru, to pay off his debts. His life took a pivotal turn after witnessing the destruction caused by the rampaging Mountain God, an incident for which the daimyo Kozuki Oden took the blame to protect him. Filled with a sense of debt and admiration, Kin'emon swore his loyalty to Oden and dedicated himself to reforming his ways to become a proper samurai and retainer. He eventually rose to become the leader of the Nine Red Scabbards, Oden's most trusted group of retainers. Following the betrayal and execution of his master by the shogun Kurozumi Orochi and the Emperor Kaidou, Kin'emon, along with several of his comrades and Oden's young heir, Momonosuke, was sent twenty years into the future by the time-manipulating powers of Kozuki Toki, Oden's wife.

Kin'emon's personality is a complex mix of deep-seated loyalty, immense pride, and an old-fashioned, often contradictory, worldview. He rigidly adheres to a traditional code of bushido, which initially manifests as extreme stubbornness and a refusal to accept help from others, especially pirates, whom he deeply distrusts. He is a man who feels shame acutely, such as when he was dismembered or struck by a woman, and he maintains his pride and formal demeanor even in the most absurd and dire situations. He holds very traditional, sexist expectations of women, believing they should be graceful and demure, which often puts him at odds with the assertive and casually dressed Nami. Despite his outrage at her behavior, he is also secretly quite perverted, and he has been known to greatly enjoy looking at her regardless. His archaic mindset also means he is unfamiliar with many concepts from outside Wano, such as Devil Fruits, which he refers to as strange sorcery, or common foods like pizza.

Kin'emon's primary and all-consuming motivation is to fulfill the last wish of his beloved master, Kozuki Oden: to liberate Wano Country from the tyrannical rule of Orochi and Kaidou and to open its borders to the world. This mission is both his driving purpose and the source of his profound loyalty. He cares for Kozuki Momonosuke, Oden's son, with a fierce and protective devotion, serving as his guardian and pretending to be his father to protect the boy's true identity during their perilous journey. After being sent to the future, Kin'emon becomes a central ally to the Straw Hat Pirates. Although he begins the story despising all pirates, his journey alongside Monkey D. Luffy and his crew forces him to recognize their honor and kindness. His role evolves from a reluctant, severed head seeking help to a key strategist who proposes the formation of the Ninja-Pirate-Mink-Samurai Alliance, culminating in the final raid on Onigashima to take down Kaidou.

His key relationships are defined by loyalty and duty. His bond with Kozuki Oden is the foundation of his character, shaping his entire life's purpose. His relationship with Momonosuke is that of a fiercely protective vassal and surrogate father figure, guiding the young heir towards his destiny as shogun. His fellow Nine Red Scabbards, including Kanjuro, Raizo, Kikunojo, and Denjiro, are his sworn brothers and comrades-in-arms, though their shared history also includes the pain of betrayal. His wife, Tsuru, is a figure from his troubled past who he deeply loves and is overjoyed to reunite with after the twenty-year separation. Finally, his relationship with the Straw Hat Pirates, particularly Sanji, Zoro, and Luffy, transforms from suspicion and disdain to deep, mutual respect and gratitude for their role in helping him achieve his impossible goal.

Throughout the Wano Country saga, Kin'emon undergoes a subtle but significant development. Initially presented as a stubborn and somewhat comical figure constantly losing his temper or his body parts, he grows into his role as a respected leader and a capable strategist for the alliance, even if his greatest tactical success comes from a fortunate misunderstanding. His pride is tempered by necessity as he learns to trust the pirates he once scorned. He confronts the painful reality of betrayal within his own ranks and steels himself to carry out his duty, culminating in a final, brutal clash with Kaidou to avenge his master and fulfill Oden's will.

As a warrior, Kin'emon possesses several notable abilities. He is a highly skilled swordsman who employs a unique technique known as the Foxfire Style, which allows him to generate fire with his slashes and, more notably, to cut through and extinguish any incoming flame or even explosion, making him a formidable opponent against fire-based attacks. He has also demonstrated the ability to use both Observation and Armament Haki, the latter being essential for him to injure the seemingly invulnerable Kaidou. Furthermore, he has consumed a Paramecia-class Devil Fruit called the Fuku Fuku no Mi, which grants him the power to create clothing and disguises for himself and others by placing a small object like a leaf or a stone on their heads and visualizing the desired outfit. This power, while non-combative, proves useful for espionage, disguise, and providing warm clothing in cold climates.