Fan Casting Attack on Titan

The plot of Attack on Titan centers on a civilization inside three walls. According to the knowledge propagated locally, it is the last location where humans still live. Its inhabitants have been led to believe that over one hundred years ago, humanity was driven to the brink of extinction after the emergence of humanoid giants called Titans, who attack and eat humans on sight. The last remnants of humanity retreated behind three concentric walls and enjoyed nearly a century of peace and the thought of venturing outside is frowned upon and discouraged. To combat Titans, the country's military employs Vertical Maneuvering Equipment, a set of waist-mounted grappling hooks and gas-powered propulsion enabling immense mobility in three dimensions.

As the series progress, the true history of the Titans and the fact that there are humans outside of the island of Paradis were revealed.