Gintama, officially billed as a "sci-fi action comedy", could be described as the Japanese version of Futurama with a dash of Ruroni Kenshin. Taking place in an alternate version of 1800's Japan, where alien invaders have suddenly shown up, they turn the capital city of Edo into an amusing anachronism of samurai and ninjas living among futuristic technologies such as flying cars, cellphones and space travel. Our story follows Gintoki Sakata, a once feared and infamous samurai, who now lazily tries to scrape together a living via odd jobs. Occasionally his past comes back to haunt him though... when he's not trying to deal with the wacky, colorful cast of characters that amass around him that is.
Gintama: The Movie is a remake of the Benizakura story arc from the beginning of season 2. Gintoki receives a job to find a cursed sword, which ends up pulling him and his friends to a conflict with enemies from his past. Benizakura is quite a bit more serious and darker than the preceding TV series, yet it still manages to balance plot and humor in a way that stays true to Gintama's style. The extra comedy bits at the end of the movie in particular are a must-see for fans of the series. Also of particular note is the excellent redone HD animation, especially in the fight scenes.