A certain ten-year-old boy has never seen the outside world. His name is Eren Yeager. Eren feels uncomfortable surrounded by people who have given up going outside of the walls for the transient peace that they are currently enjoying. Eren refers to them as livestock while they refer to him as an outsider.

However, one day that all changes when a Giant Titan appears suddenly smashing to pieces both Eren’s ‘dream’ and society’s ‘peace...’

After defeating the Armored Titan (Reiner), the Colossus Titan (Bertolt), and the Beast Titan (Zeke), Eren and the other humans within the wall have succeeded in retrieving Wall Maria and in eliminating the titans outside the wall. Also, the titans are found out to be the people of Eldian, who is the same race as the people in the wall, being changed by the people of Marley.

Four years has passed after the incident. The war with the Middle East Alliance, which Marley has started after the failure of retrieval of "original titan" by Reiner and the others, has ended.
Zeke, who leads Eldian army, recommends again to the headquarter of the army for retrieval of "original titan", under the reason of making the rule by the titan power the absolute.
Reiner meets Falco's old friend, Kruger, but...