The show throws you into a mass hallucination where everyone you know has become an alien version of themselves, then spends fifty episodes mining comedy from the gap between who they were and who they've become. Every joke lands because it assumes you've watched season one; there is no mercy for new viewers. You come for the absurdist premise, stay because the character work underneath never stops being real, and leave having watched Gintama prove it can destroy itself and rebuild funnier than before.

Shinpachi returns to Edo after a year away and walks into complete chaos. Gintoki and Kagura have become strangers, acting nothing like themselves. His sister Otae is married to Kondou and expecting a baby. Everyone in the city has changed drastically, in looks and in personality. Bewildered, Shinpachi joins the Shinsengumi at the request of Otae and Kondou, and finds even more transformations there. Only Hijikata remains unchanged, and the two team up to restore Edo to the way they remember it. Beyond that opening, the Yorozuya carry on with more misadventures in their alien-filled Edo, full of crude jokes, parodies and cheeky references, mixing action, comedy and drama with a science fiction backdrop.