Attack on Titan

It is set in a world where humanity lives in cities surrounded by enormous walls; a defense against the Titans, gigantic humanoids that eat humans seemingly without reason. The story initially centers on Eren Yeager and his childhood friends Mikasa Ackerman and Armin Arlert, who join the military to fight the Titans after their hometown is invaded and Eren's mother is eaten and Eren swears to avenge her. However, as the story progresses and the truths about the Titans are slowly revealed to the reader, the narrative shifts to encompass Historia Reiss, squad leader Levi, Eren's father Grisha, and other supporting characters.