"Gintama: Shiroyasha Kōtan" is a two-episode anime special that serves as a condensed retelling of key events from the early arcs of the main "Gintama" series. The narrative centers on Gintoki Sakata, a lazy yet skilled samurai who runs the Yorozuya, a freelance odd-jobs business in an alternate Edo period where aliens, known as Amanto, have taken over Japan. Gintoki is joined by Shinpachi Shimura, a glasses-wearing teenager, and Kagura, a superhumanly strong alien girl from the Yato clan. Together, they navigate a chaotic world filled with humor, action, and emotional depth.

The story begins with Gintoki and his companions taking on various odd jobs, often leading to absurd and comedic situations. However, the tone shifts when they encounter the Shinsengumi, a police force tasked with maintaining order in Edo. Gintoki’s past as a legendary samurai, known as the "Shiroyasha" (White Demon), resurfaces, revealing his involvement in the Joui War, a failed rebellion against the Amanto. This backstory intertwines with the present as Gintoki faces off against former comrades and enemies, including the sinister Nizou Okada, who seeks revenge for past grievances.

The special highlights Gintoki’s internal struggle between his carefree present and his violent past, emphasizing his commitment to protecting his newfound family and friends. The narrative also explores themes of loyalty, sacrifice, and the consequences of war, all while maintaining the series' signature blend of comedy and drama. Key supporting characters, such as the Shinsengumi members Hijikata and Okita, play significant roles, adding depth to the story’s conflicts and alliances. The special concludes with a climactic battle that underscores Gintoki’s resolve to live by his own principles, even in a world that has drastically changed.