Gintama Opening - Katte ni My Soul
The world is invaded by aliens, government has forbidden swords and last samurais fought against aliens and corrupt government have put their swords away. Gintoki, being one of those samurais, tries to get used to his new life with Kagura and Shinpachi.
The anime consists of independent episodes which are generally funny parodies of other anime but there are some arcs about the main plot and background stories of characters with outstanding fights and action. Fans are currently waiting for the final season to complete the whole story.