(Even though I'm sure if you haven't watched this you have at least heard of it)

Over a hundred years ago when giant human like beings called Titans, who eat humans appeared, humanity took a stand by building three 100 meter high walls, each spread 250 miles apart.

The outermost wall was called wall Maria , the second, wall rose, and the third and innermost where the richest people lived was called wall Sheena.( if you know the anime and think I spelled it wrong, that is the way it's spelled in the manga)

They invented 3d maneuver gear, to kill the quick regenerating Titans, (when the were hurt the wound would close in less than two minutes, even if you blew their heads off) by cutting the nape of their necks, the only spot that they couldn't regenerate from.

But when a mutant Titan that is so big it towers over the wall appears and breaches the wall.

For the first time in a hundred years, humanity is reminded of the dangers of ever thinking that they were safe, and that the world though seemingly beautiful is not a fair place.

----------------warning----------------------
This anime is extremely sad, and involves a lot of death and gore.