Set in a parallel universe around the Edo period.
Alien species Amanto attack planet Earth. The people on Earth fight back against the aliens for more than 10 years. The Shogunate sees the power of Amanto and decide accept their conquest. The Shogunate builds a puppet government for Amanto and carry out the Sword Abolishment Edict. Due to these actions, samurai, that fought against the Amanto for their country and their lord, fall into a decline.
Gintoki Sakata (Shun Oguri) is a samurai and happens to meet people. He has an extraordinary experience. (http://asianwiki.com/Gintama)
OAL: This was was absolutely hilarious and well done, but I am not familiar with the source material. I am planning on rectifying that.
i haven't been able to re-find it.