In the wake of Eren Yeager's cataclysmic actions, his friends and former enemies form an alliance against his genocidal rampage. Though once bitter foes, Armin Arlert, Mikasa Ackerman, and the remaining members of the Scout Regiment join forces with Reiner Braun and the survivors of the Marleyan military. Their meager united front sets out on a mission to stop Eren's wrath and—if possible—save their old comrade in the process.

As Eren pushes forward at any cost, he battles his own internal turmoil. Although he feels immense remorse over his horrific invasion, Eren believes he harbors noble intentions: he believes the path ahead is the only way to save his friends and, to a greater extent, his people.

The opposing battalions spiral toward an inevitable final clash that may claim the lives of millions. Though they face an army of monsters beyond anything they could have previously imagined, Mikasa, Armin, and their allies stand brave in the face of certain doom.