Gintama, is a Japanese manga written and illustrated by Hideaki Sorachi and serialized, beginning on December 8, 2003, in Shueisha's Weekly Shōnen Jump. Set in Edo which has been conquered by aliens named Amanto, the plot follows life from the point of view of samurai Gintoki Sakata, who works as a freelancer alongside his friends Shinpachi Shimura and Kagura in order to pay the monthly rent. Sorachi added the science fiction setting to develop characters to his liking after his editor suggested doing a historical series.
The story is set in the late Edo Period. Humanity is attacked by aliens called "Amanto" (天人, "Sky People"). The samurai of Japan join the battle against the aliens, but when the Shogun realizes the power of aliens, he betrays the samurai and surrenders to the aliens. The Shogun writes an unequal contract with aliens which allows the aliens to enter the country and places a ban on carrying swords in public. The swords of samurai are taken away so they can no longer resist the aliens. After that the Shogunate becomes a puppet government.
(https://en.m.wikipedia.org/wiki/Gin_Tama#Themes_and_style)
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