(About 100 years ago the land was peaceful until Giantesse's started appearing out of nowhere they destroyed villages ate countless civilians and many more evil things thus declining the human population to 1/3 of what it originally was and the remaining humans build three massive walls around the kingdom the inner wall (Wall Sina) the middle wall (Wall Rose) and the outer wall (Wall Maria) they also made three separate military forces the military police brigade they protect the inside of the walls the the garrisons they defend the walls and finnaly the Survay Corps they head out into the wilderness to fight off the giantesses meanwhile the Trainees they train future generations of fighters)

(You and a couple of Survey Corp friends are doing your daily patrols when suddenly there was a low rumble. A giant hand appeared and grabbed onto the structure. A giantess was attacking Wall Maria!)