|If Eren is only attacking onward like he said he would... this resistance is coming from Ymir. In that case, the Founder wants to massacre all of humanity too... Ymir, the Founder... is invincible... There's nothing... we can do... Is this... where... it... all ends... for us...?|
|— Armin ponders Ymir's power and motives as his consciousness fades|
Armin Arlert steels himself to transform into his Colossus Titan, having realized the defeated Beast Titan was a dummy, but is swallowed by a Titan. Before the group can rescue him, an army of previous incarnations of the Nine Titans materialize on Eren Yeager's back. Outside Fort Salta, Onyankopon is left unconscious by his crash landing, and the Marleyan general orders his soldiers to fire on the Titans.
Pieck Finger goes to detonate Eren's nape, but fails when her Titan is skewered by a War Hammer Titan. Inside of the Titan, Armin despairs as he realizes Ymir must also wish for mankind's eradication. Meanwhile, the Titans' assault on the group overwhelms them, and they scramble to save one another while their strength and gear fails. As Mikasa Ackerman prepares to make a last stand, the group is whisked away by a winged Titan. The soldiers are greeted by Annie Leonhart, who expresses that she could not stay away after learning of Falco Grice’s ability.
In the middle of the night, 2000 years ago, Ymir Fritz releases a group of pigs from their pen.
As the Beast dissolves, Levi realizes that Zeke is not inside it. Aghast at the idea of searching Eren’s entire Titan for Zeke, Jean and Armin agree that Armin should transform into his Colossus Titan and use the resulting explosion and its devastation as a means of locating Zeke. Mikasa begins to object, but Armin reassures her that the explosion will not be large enough to kill Eren. Reminding himself that he must be willing to make sacrifices to achieve his goals, Armin steels himself and prepares to transform. The group begins to retreat to a safe distance but turn around to see Armin's being devoured by a Titan. As Armin is being swallowed, he is caught off guard at the sight of Ymir's watching him in the distance. The group tries to return to him but is blocked by an army of Titans that materialize on Eren’s back.
Outside Fort Salta, Mr. Leonhart and a group of Liberio survivors pull Onyankopon from the wreckage of the flying boat. Desperate for news from Paradis, Mr. Leonhart tries to wake Onyankopon to ask him about Annie. In Salta’s control tower, the Marleyan general orders his remaining soldiers to fire cannons at the Titans. His soldiers point out that they only have enough men remaining to fire three cannons, but the general insists that they do whatever they can to help.
Reiner is quickly swarmed by three of the Titans and is saved by Jean, Mikasa, and Connie. Jean quickly realizes that the Titans are behaving too intelligently to be Pure Titans. Connie begins to panic over Armin; but Levi reassures him, pointing out that Armin would have transformed if he had sustained injury. Levi assumes that Armin is being transported to the back of Eren’s Titan, where he will not be able to do any harm, but advises his squad not to brashly rush after him. Levi suggests using himself as a distraction for his squad to pursue Armin, but Pieck stops him by revealing that the Titans they are facing are resurrected versions of the Nine Titans from throughout the ages.
Theorizing that the power of the Founding Titan can infinitely respawn copies of the Nine Titans, Pieck chooses to charge Eren’s nape alone in an attempt to blow it up with the bombs from the flying boat. As Pieck manages to set the bombs and prepares to detonate them, her Titan is impaled by a resurrected shell of Will Tybur’s sister's War Hammer Titan. Reiner tries to help Pieck but is attacked from behind by Porco Galliard’s Jaw Titan. Jean tries to help Reiner but is nearly eaten by Marcel Galliard’s Jaw Titan, only narrowly being saved by Levi. Levi orders his squad to make a push for Armin, as they no longer have any way of winning without him.
Inside the Titan that devoured him, Armin begins to suffocate and wonders if Eren is going to kill him. Remembering the glimpse he caught of Ymir, Armin realizes that she is likely the one responsible for the massive Titan resistance with which his allies are being met. Theorizing that Ymir also wants humanity to be wiped out, Armin despairs, lamenting that Ymir is too powerful for them to oppose. Unable to move, Armin sees a vision of a crying Bertolt Hoover, after which a resurrected shell of Bertolt's Colossus Titan assaults the group on Eren's back, nearly devouring Reiner before he is rescued by Jean.
The Colossus flings Reiner’s inert Titan at the rest of the squad. Connie is knocked unconscious by the impact, and Mikasa is forced to guard his body from attacking Titans while Levi is too weak from his injuries to be of more assistance. Both Jean and Reiner’s vertical maneuvering equipment are too damaged for use, and they are left hanging helplessly from Eren’s Titan. As Mikasa defends them from nearby Titans, Reiner orders Jean to let him go so he can transform again, but Jean points out that he will just be crushed underfoot by the Colossus Titans marching beneath Eren’s Titan. Reiner asks Jean if he thinks they will be able to win, and Jean admits that they probably will not; nevertheless, he reiterates his desire to keep fighting.
Mikasa sees another Titan attempting to eat Connie but is too far away to reach him. Gathering the last of his strength, Levi manages to slice the Titan's eyes and blind it. However, the Titan bites down on his leg before he can escape. Mikasa slices the Titan’s nape before it can crush Levi’s leg, and Connie regains consciousness in time to save Levi from falling to his death. Mikasa and Connie return to Jean and Reiner with Levi as the army of Titans begins to surround them. Growing desperate, Mikasa prepares to make a last stand against the Titans. However, a winged Titan suddenly appears and whisks the group away at a pace too swift for the encroaching Titans to catch them. As the Titan flies them to safety, the bewildered soldiers are greeted by Annie, who proclaims that she was unable to stay away from the battle after learning that Falco’s Jaw Titan had the ability to fly.