The story takes place in Edo (known today as Tokyo because of the name change in 1868), Japan, which has been taken over by aliens called Amanto since the late Edo period. The samurai of Japan have fallen, and the Amanto placed a ban on carrying swords in public. The story focuses on an eccentric samurai with a natural perm, Sakata Gintoki, his (partial) apprentice Shimura Shinpachi, and a teenage alien girl: Kagura. All three are "free-lancers" who search for work in order to pay the monthly rent, which usually goes unpaid anyway.