Gintama

Twenty years ago, Edo-period Japan suffered a great cultural shock—the aliens called Amanto invaded the Earth, overpowered the nation's government, and outlawed the carrying of swords by the once proud samurai. Moreover, the aliens took the people's jobs and are currently running Japan as a sweatshop using the natives as laborers. In this strange new era are Gintoki Sakata, an eccentric samurai whose personal trademarks are his naturally permed silver hair, his love of anything sweet, and his addiction to <i>Shonen Jump</i>; Shinpachi Shimura, the teenaged heir of the Kakido-Ryu style; and Kagura, an incredibly strong alien girl from the powerful Yato clan. The trio are self-employed in an odd jobs shop called Yoruzuya Gin-chan, which offers to do almost anything for a price, from finding lost kittens to saving the world. Unfortunately, the jobs rarely go as planned, or pay enough to cover the pain and suffering the employees encounter—never mind their rent.

Synopsis from Anime News Network