Set in an alternate Edo period where Earth has been conquered by alien beings known as Amanto, "Gintama" blends historical fiction, science fiction, and comedy into a unique narrative. The Amanto have imposed a ban on carrying swords, stripping samurai of their traditional status and power. The story centers on Gintoki Sakata, a former samurai who now works as a freelancer, taking on odd jobs to make ends meet. Gintoki is joined by Shinpachi Shimura, a glasses-wearing teenager seeking to restore his family's dojo, and Kagura, a superhumanly strong alien girl from the Yato clan. Together, they form the Yorozuya, a small business that accepts a wide range of requests, from mundane tasks to dangerous missions.

The series is episodic in nature, often shifting between comedic, slice-of-life episodes and more serious, plot-driven arcs. Gintoki’s past as a samurai who fought in the Joui War against the Amanto is gradually revealed, adding depth to his character and the overarching narrative. Key figures from his past, such as the enigmatic Shinsengumi police force and former comrades like Katsura Kotarou and Takasugi Shinsuke, frequently intersect with the Yorozuya’s adventures. The Shinsengumi, led by the stoic Isao Kondo and his subordinates Hijikata Toshiro and Okita Sougo, often clash with Gintoki and his group, though their interactions range from antagonistic to cooperative depending on the situation.

Themes of loyalty, identity, and resilience are explored as the characters navigate a world where traditional values clash with alien influence. Gintoki’s laid-back demeanor and love for sweets and manga often mask his deeper sense of justice and commitment to protecting those he cares about. Shinpachi serves as the moral compass of the group, while Kagura’s childlike innocence and immense strength provide both comedic relief and moments of emotional weight. The series also delves into the struggles of other characters, such as the Shinsengumi’s internal conflicts and the motivations of antagonists like the Kiheitai, a rebel group led by Takasugi.

As the story progresses, the tone shifts more frequently toward action and drama, particularly during major arcs that reveal the consequences of the Joui War and the true nature of the Amanto’s presence on Earth. The narrative balances its humor with poignant moments, exploring the impact of loss, the importance of found family, and the resilience of the human spirit. Through its eclectic mix of genres and tones, "Gintama" creates a rich, multifaceted world that appeals to a wide audience.