Attack on Titan: a not so long time ago, titans appeared from out of nowhere and began to hunt down and destroy humanity. They have incredible regenerative powers so the only way to kill one completely is to sever the spine at the base of the neck. Humanity has been pushed back to one stronghold, a system of 3 giant walls in a circle, an outer, middle, and inner wall. For the most part giants aren't intelligent at all, but somehow they only attack and kill/eat humans. They don't actually need to eat to survive either and the method of reproduction is unknown. Few females have been spotted among the giants but all the giants lack genitalia. Then there are the random enigmatic ones that seems smarter and better coordinated than the others, and they're even harder to kill. So humanity is left to live within the walls, while brave soldiers slinging around like steampunk batmen with katanas venture out to try to take back land for humans, but have been vastly unsuccessful so far. Things are about to change as the anime begins to pick up and mysteries begin to slowly reveal themselves.