For over a century, humans have been living in settlements surrounded by gigantic walls, which prevent the Titans, giant humanoid creatures who eat humans, from entering. Young Eren Yeager wishes to see the outside world by joining the Recon Corps, as he likens living in the cities to livestock. Despite this, his foster sister Mikasa Ackerman and their mother Carla are against him in joining the Corps. Even after seeing the Recon Corps returning home with large casualties, Eren expresses his interest to join.