|Hear me, all Subjects of Ymir. My name is Eren Yeager. I now speak to all Subjects of Ymir by way of the Founding Titan's power. Every wall on the island of Paradis has been undone. All of the Titans buried within them have begun their march. My goal...is to protect the people of Paradis, the land where I was born and raised. But the world desires the extinction of the people of Paradis. Over countless years, the world's hatred has grown beyond even the bounds of this island. The people of the world surely will not stop until they have killed every last Subject of Ymir. I reject those wishes. The Titans of the Walls will thunder across the world, to every land beyond this island. Their rumbling feet will snuff out every life in those lands.|
|— Eren's message to all Subjects of Ymir|
The Survey Corps explores Marley for the first time and learn about the political situation in the outside world. Eren Yeager is quick to pick up on the injustices that the minorities in Marleyan society suffer, whether they are Eldians in the internment zone or immigrant refugees. Hange Zoë hopes to find allies so they can declare Paradis Island's desire for peace and avoid having to go along with Zeke Yeager's plan, but that hope is dashed when the "Association to Protect the Subjects of Ymir" makes it clear that they still consider the Eldians on the island to be worthy of hate.
Back in the present, Eren has unleashed all of the Titans of the Walls. Armin Arlert realizes it is far more than needed if Eren's only intent is repelling the current invasion. Mikasa Ackerman wonders if Eren has always been this way and they never noticed, or if there was something different they could have done or she could have said to avoid coming to this moment. Using the power of the Founding Titan, Eren announces his intention to kill everyone in the outside world in order to protect the people of Paradis.
Mikasa Ackerman remembers when she and the other members of the Survey Corps went abroad for the first time. Though everyone has said that Eren Yeager has changed, she wonders if that is true and perhaps he has been the same person the entire time.
When the Survey Corps arrives in Marley, the soldiers are disguised to blend in with the local population but they are surprised to see towns and people beyond the Walls. Onyankopon greets them and offers to guide them to Kiyomi Azumabito's estate. Connie Springer, Sasha Blouse, and Hange Zoë are shocked to see a car for the first time, and behave as though it is some kind of animal. Levi Ackerman encourages Onyankopon to intervene before they try feeding one carrots.
In the middle of this, Mikasa finds Eren staring off into the distance. Armin Arlert tries to get Eren to liven up by reminding him that they are finally in the world outside the Walls, but Eren does not seem excited about it due to the fact that he has already seen most things through his father's memories. Mikasa wonders whether nobody had realized that Eren had changed or whether they had not wanted to notice the changes.
The Survey Corps samples ice cream for the first time, and Mikasa encourages Eren to try it. He recognizes it immediately, once again, due to his father's memories, but also remembers that Eldians in the internment zone rarely get to eat it.
As they take in the sights, Levi catches a young boy with a fez lifting Sasha's purse and tells the kid that it does not belong to him loud enough that others overhear. The Marleyan crowd takes it poorly. The boy is an immigrant who does not speak their language, and the Marleyans assume he must have snuck aboard a ship and discuss making an example of him to discourage others.
Sasha tries to intervene, saying that she has her purse back so no damage is done, but the Marleyans are still hostile and insinuate that the boy could be a Subject of Ymir who slipped in from another country. Seeing the boy's fear, Levi scoops him under one arm and clarifies that he never said the child was a pickpocket and the purse is his older sister's. Nobody buys the excuse, but Levi and the other soldiers run off with the boy. Though happy to be free, the boy thanks Levi by stealing his purse before leaving.
At Kiyomi's estate, she listens to the story of what happened to them along the way and confirms that blood testing has improved, and as a result of that, Subjects of Ymir who have escaped internment are constantly being discovered. Being a Subject of Ymir used to be proof of one's status in society, but when the Eldian Empire crumbled, those same people were chased out of their own countries. Because of this, Kiyomi says it will be difficult for them to form friendly relationships with other nations.
Armin is still hopeful though, so they avoid implementing Zeke Yeager's plan and Historia Reiss will not have to bear children to serve as royal-blooded Titans. Hange wants to observe the "Association to Protect the Subjects of Ymir" in hopes that they will be friendly enough for Paradis Island to declare they seek peace.
Mikasa notices that Eren has left their meeting with Kiyomi and goes outside to look for him. She finds him looking at a cluster of refugee tents. At first, she begins to reprimand him for going outside alone when he is their enemies' most wanted target, but then she realizes that he is looking at the boy who stole from Sasha and Levi, as well as the boy's family.
Eren tells her that these tents are where these people live after losing their homes to war. The people here are like the two of them. One day life stopped being normal and everything was taken away. He asks Mikasa why she cares about him so much, whether it is because he saved her when they were kids, or because they are family. Mikasa stammers and begins to say that he is family, when the boy's father walks up to them.
The man offers them something warm to drink as the rest of Eren and Mikasa's friends find them. Disappointed at the timing, Eren instead gestures that they all should join him and the refugees. They enjoy a meal together and after the two groups warm up, it turns into a party. Jean and Connie run out to bring more alcohol, and other refugees join the group. Mikasa and Armin have a good time while Eren smiles. Eventually, Hange, Levi, and Onyankopon find their soldiers passed out among the refugees.
Later, the forum for the "Association to Protect the Subjects of Ymir" goes poorly. A speaker defends only the Subjects of Ymir who are not Eldian, and tells everyone to reserve their hatred for the "devils" of Paradis Island.
Mikasa realizes that was the day that Eren left their side. Later, they would receive a letter from him saying that he would entrust everything to Zeke. She wonders if there was any other choice they could have made, or if she had answered differently when Eren had asked her what he meant to her, that could have avoided the battle they find themselves in now.
In the present, Mikasa and Armin are in the ruins of Shiganshina District after the Walls have crumbled and the Titans of the Walls have broken free. In the distance she sees a massive skeleton that dwarfs even the newly freed Titans and notices that it seems to have appeared where Eren was. Beside her, Armin shouts to make himself heard over the Rumbling and tells Mikasa that Eren must have control of the Founding Titan. He believes that Eren will use it to stop Marley's invasion. But as Armin looks around, he realizes that it is not just the Wall around Shiganshina that has been destroyed, but the rest of Wall Maria, which is unnecessary if all Eren intends to do is repel the current attack.
Eren then reaches out to all Subjects of Ymir by using the Founding Titan's power. His voice reverberates in their minds and he explains that he has unhardened all the Walls on Paradis, freeing the Titans within them. He intends to protect the people of Paradis, because its people gave birth to him and raised him. However, the rest of the world desires their extinction, and Eren cannot abide by that, so he intends to trample the lands beyond the island until all life beyond Paradis has been eliminated.