Over 100 years ago, a natural predator of humanity appeared: the Titans, giant humanoid but mindless monsters whose sole purpose of existence seemed to be to devour humans. There was an insurmountable gap in power between them and mankind, and as a result, humanity was rapidly exterminated to the brink of extinction. The survivors responded by constructing three concentric walls: Wall Maria, Wall Rose and Wall Sina, which graced them with a century of peace.