Gintoki Sakata is the central character of his narrative, a former revolutionary samurai who now operates a small, freelance odd-jobs business called the Yorozuya in a version of Edo that has been transformed by the presence of extraterrestrial beings. His full name, Gintoki, directly informs the series title, and his character is a deliberate subversion of the traditional heroic archetype. As a child, Gintoki was an orphaned scavenger on a war-torn battlefield, a period where he was known as the "Corpse-Eating Demon." He was found and taken in by the wandering teacher Yoshida Shouyou, who provided him with a home and an education at his private school. There, Gintoki formed profound, lifelong bonds with two other students, Kotaro Katsura and Shinsuke Takasugi. When Shouyou was unjustly arrested, the three students joined the Joui War, a fierce conflict against the invading Amanto, to rescue their mentor. On the battlefield, Gintoki's terrifying skill, silver hair, and white coat earned him the legendary moniker "Shiroyasha," or White Demon.

The war ended in tragedy when Gintoki was forced by the enemy to personally execute his teacher in front of his comrades to spare their lives. This traumatic event shattered their group, and Gintoki drifted into a life of poverty and idleness. He began living in the back room above a bar owned by Otose, a landlady he promised to protect after he stole food from her husband's grave memorial. To make a meager living, he established the Yorozuya, a service that will take on any task for a price, no matter how mundane or bizarre. Over time, he was joined by two unlikely partners: Shinpachi Shimura, a kind-hearted boy trying to uphold his family's samurai dojo, and Kagura, a superhumanly strong alien girl from the Yato warrior race. Together, this makeshift family takes on odd jobs, often getting entangled in conflicts that shake the very foundations of their society.

On the surface, Gintoki is the picture of an unmotivated and irresponsible adult. He has a permanent five o'clock shadow, a natural perm of silver hair, and a pair of lifeless, "dead-fish" eyes. His defining traits are a crippling addiction to sweets, especially chocolate parfaits and strawberry milk, which a doctor has warned him is leading to diabetes, and an obsessive love for Weekly Shonen Jump magazine. He is perpetually late on his rent, spends his meager earnings on pachinko gambling, and has an irrational fear of ghosts and the dentist. He often behaves like a lazy coward, speaking with a lecherous and crude sense of humor, and is known for a sadistic streak he shares with the police officer Sougo Okita. Despite these flaws, Gintoki possesses an unwavering and deeply personal samurai code. He forgoes grand ideals about country or honor, fighting solely to protect the people and things he cares about in the present, a direct result of the loss he suffered in his past. When someone he values is threatened, or when he witnesses injustice against the weak, his demeanor undergoes a complete transformation into a calm, decisive, and extraordinarily powerful warrior.

His motivations are rooted in atonement and the preservation of a new family. He lives with the heavy guilt of having killed his beloved teacher and failing to protect his comrades. To cope, he has built a new life centered on the Yorozuya, and his primary driving force is to defend Shinpachi, Kagura, and everyone else who has come to rely on him, swearing to never lose anyone important again. This places him in a unique position as a stabilizing force in Edo, attracting allies and rivals alike. His key relationships include a deep, unspoken bond with Shinpachi and Kagura, who serve as his anchors to a peaceful life and remind him of his own humanity. He maintains a complex, antagonistic friendship with Toshiro Hijikata of the Shinsengumi, as the two share an uncanny parallel in their thinking despite constant bickering. His former classmates have diverged drastically from his path; Katsura remains a somewhat comedic fugitive terrorist, while Shinsuke Takasugi has become a nihilistic and destructive force, blaming Gintoki for their teacher's death and seeking to destroy everything.

Throughout the narrative, Gintoki's character development is not about gaining new power, but about coming to terms with his traumatic past and embracing his present role. He initially appears cynical and disconnected, but his actions consistently draw him into larger conflicts, forcing him to confront old friends and enemies. Over time, he stops running from his past and actively seeks to help those he once fought alongside, even Takasugi, showing a maturity that comes from accepting his failures rather than being consumed by them. His journey is one of learning to live with his scars and finding a new purpose, not as the legendary Shiroyasha, but as the leader of the Yorozuya.

As a combatant, Gintoki is a master swordsman of immense power, though his skills have dulled slightly from his war days due to a lack of serious fighting. His style is described as rough, wild, and instinctual rather than technical or graceful, but it is devastatingly effective. His signature weapon is the "Lake Toya" bokuto, a wooden sword he claims is made from a 10,000-year-old tree but is, in fact, a cheap mail-order item he constantly breaks and replaces. Despite its origin, he wields it with such force that it can cut through metal, deflect energy beams, and shatter solid objects. He is capable of feats of incredible endurance and speed, able to fight for extended periods while suffering severe injuries, and has shown the ability to disrupt an enemy's precognitive senses with his sheer willpower and chaotic killing intent. He is also a cunning strategist, often using trickery and psychological manipulation to gain the upper hand in a fight, and possesses a strange spiritual sensitivity that allows him to see, interact with, and even exorcise ghosts.