Attack on Titan Season 4

Instead of progress, humanity found itself thrown back by the appearance of a race of giants. These enormous humanoids lacked both speech and reason, but they devoured people like chips, and conventional weapons of the 19th century proved powerless. The remnants of the human race were able to survive only behind colossal walls that encircled the last fields, cities, and villages with a triple ring. The lull lasted for a hundred years, during which people calmed down, the army was reduced, and the city guard turned into idlers. The only fighting force that remained was the Recon Corps, but who needs suicidal individuals who constantly risk their lives outside the walls when you can sit comfortably behind a stone fence?