Gintama: Nanigoto mo Saisho ga Kanjin nanode Tashou Senobisuru Kurai ga Choudoyoi

Aliens known as Amanto have transformed Edo and pushed the samurai into an age where carrying swords is forbidden. Kotarou Katsura refuses to accept their rule and prepares an attack with a giant machine, hoping to strike at the Shinsengumi and restore pride to the fallen samurai.

Gintoki Sakata has concerns of a far less revolutionary kind: he only wants to enjoy cherry-blossom viewing with Shinpachi and Kagura. When the Shinsengumi claims the same spot, the argument escalates into a ludicrous contest where rock-paper-scissors becomes far more violent than intended. Katsura's grand scheme and the two groups' petty rivalry soon collide in the chaotic way only Edo can manage.