Attack on Titan is a Japanese manga series written and illustrated by Hajime Isayama. The series began in Kodansha’s Bessatsu Shōnen Magazine on September 9, 2009, and has been collected into 20 volumes as of August 2016. 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, his adopted sister Mikasa Ackerman and childhood friend Armin Arlert, who join the military to fight the Titans after their home town is invaded and Eren’s mother is eaten. 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, and other supporting characters.