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Liberio (レベリオ Reberio?, also translated as Rebellio) is a Marleyan city containing an internment zone (収容区 Shūyō-ku?), an area of land designated by Marley for people of Eldia to live in, separate from the rest of the population.
At the end of the Great Titan War, King Karl Fritz and many Eldians settled on the island of Paradis, fleeing from the mainland war. However, some Eldians stayed behind on the continent were overtaken by Marley, the enemy nation.
Rather than slaughtering the remaining Eldians on the continental mainland, the nation of Marley chose to isolate the Eldians into designated internment zones. While Marley claimed to be extending mercy towards the devil's descendants, the internment zones were in reality created to store Eldians until the Founding Titan could be acquired from the King of the Walls on Paradis in the future. Around this time, a statue to the Marleyan hero Helos is built.One of the internment zones established on the mainland was within the city of Liberio. In Grisha Yeager's childhood, he and his family lived a quiet life in Liberio until Grisha decided to wander beyond the internment zone walls with his sister Faye without authorization. They were found by Public Security Authority officers Kruger and Gross, the former punishing Grisha while the latter claimed to escort Faye back to Liberio. In reality, Gross had taken Faye to his home and fed her to his sons' dogs, leaving her corpse by the river near Liberio. This event shattered Grisha's respect for his unresponsive father and kindled a self-hatred over his foolish decision.
After some years had passed, Grisha joined the Eldia Restorationists, a secret rebellious group in Liberio who, while cooperating with the Eldian spy under the alias "the Owl", sought to restore Eldia's former glory. There he met Dina Fritz, the last descendant of the members of the royal family which remained behind on the mainland after the war. Grisha married Dina a year after joining the Restorationists, and together they became the parents of a child named Zeke, whose royal blood Grisha planned to exploit for Eldia's favor in the future.
Years later, the Marley government announced to the people of Liberio that a warrior program would accept Eldian children between the ages of five to seven to inherit the powers of the seven Titans that Marley had taken during the war. Seeing an opportunity, Grisha sent his son Zeke into the warriors to act as a double agent for Eldia. However, when Zeke turned seven, he turned the Eldia Restorationists in to the Public Security Authorities, who arrested them all and sent them away to the island of Paradis to become mindless Titans.
A decade after the capture of the Eldia Restorationists, Gabi Braun was born in the Liberio Internment Zone.
Before the Paradis Island Operation, Reiner Braun, Bertolt Hoover, Annie Leonhart, and her father lived their days in Liberio, a place which Reiner and Bertolt would later refer to only as their "hometown". Before Annie's departure from Liberio, her father ensured her that he would support her even if all the world hated her, and that he would only ask that she would return home.
During their days spent in the 104th Training Corps, Reiner and Bertolt claimed that their hometown lied in the southeastern mountainous region of Wall Maria and that their town had been overrun by Titans without warning during the fall of Wall Maria. Reiner in particular expressed a strong desire to return to his hometown in the future.
During the Wall Rose invasion when the Survey Corps recruits battle the Titans at Utgard Castle, Reiner comes close to death by a Titan and fears for the end of his life before he is saved by Bertolt. At this time he strengthens his will, filled with determination to return to his hometown. He shares his resolve with Bertolt, who understands the true meaning of what Reiner says and agrees with his hopeful words.
The next morning, when Reiner begins to lose hope for his situation due to an injury inflicted on his arm at Utgard, Bertolt encourages him by reminding him of their imminent return to their hometown. Not long afterwards, the two reveal their Titan identities as the Armored and Colossus Titans and attempt to capture Eren Yeager, whom they must bring to their hometown as part of the plan to regain the Founder. They succeed in capturing him and escape to a Titan Forest.
While in the Titan forest, Reiner reminds Bertolt that their most favorable course of action is to return Annie Leonhart, Historia Reiss, and the "Coordinate" to their hometown in order for their mission to be complete. Reiner also suggests that Bertolt should confess his true feelings to Annie upon their return, but Bertolt denies any such affections. Later, when Reiner and Bertolt attempt to escape with their captives Eren and Ymir, they inform the others that Eren's life is not up for negotiation and that he is going to be taken to their hometown. Armin taunted Bertolt at the thought of leaving Annie behind, causing him to attempt an attack and exposing a vulnerable moment for Erwin Smith to free Eren.
Ymir and the fleeing Warriors arrive in the ruins of Shiganshina District later that night, where Reiner lets Ymir know that her rescue is hopeless if they take her to their hometown. Ymir accepts her fate, believing that she owes Reiner and Bertolt a favor for indirectly freeing her from her life as a Titan five years before.
In the aftermath of the battle of Shiganshina District, the surviving members of the Survey Corps learn of the existence of Liberio and the rest of the outside world through Grisha Yeager's autobiographical writings, kept hidden in the basement of his former home.
Four years later, the nation of Marley wins a victory against the Mid-East Allied Forces. Gabi Braun, a candidate to inherit the Armored Titan, as well as her other warrior cadet comrades, are later told that they will soon be able to return to Liberio, their hometown.
The Eldian forces from the Marley Mid-East War return to Liberio by train. After arriving, the Eldians are chaperoned through the city, back into the Liberio internment zone by Commander Magath, and reunite with their families. The injured Eldian soldiers are also taken to the quarantine zones hospital. Among these injured soldiers is 'Mister Kruger'. Warrior cadet Falco Grice meets Mister Kruger, and delivers numerous letters back and fourth for him in an unregulated postbox outside the internment zone.
The Tybur family visit Liberio in order to see the statue to Helos at the headquarters. The head of the family, Willy Tybur, meets Commander Magath and together they give their allegiance to each other to reform Marley.
One month later, Willy calls upon the world's nations to hold a festival in Liberio, where he would reveal how to solve the problem of Titans. Before the festival, he meets with Magath to discuss the progression of the plans to reform the military. The two also show awareness that Marley has been infiltrated, and create the plan to bait an attack from Paradis.
The day before the festival, multiple nations foreign ambassadors come to Liberio, and enjoy wine and finery served by the warrior cadets. They are addressed by Willy concerning his plans to reveal all in the quarantine zone the next day.
The Liberio festival is held, with numerous people setting up stools in order to impress foreign visitors. The people of the internment zone also partake in the celebration over the course of the day. At night, crowds of civilians, army officials, and foreign ambassadors gather to hear Willy's speech. Before the curtain rises, Falco asks for a moment of Reiner's time, and leads him to a basement where 'Mister Kruger', identified as Eren, awaits.
The curtain rises and Willy takes the stage, beginning his speech with a production recounting the history of the world, and the horrors of the Titans. In an interlude, Warriors Pieck and Porco Galliard are summoned by a soldier of unknown allegiance, tricking them and trapping them into a Warrior confinement area. When Willy Tybur returns to the stage, he reveals that the understood history of the world is in fact a lie. He explains that it was a fabrication perpetuated by the Tybur family on behalf of the true hero to the world, the peace-seeking Karl Fritz. Despite this fact, Willy explains to the crowd that a threat to world peace has now appeared, that threat being Eren Yeager.
Meanwhile, Eren commands Reiner and Falco to remain in the room by threatening the civilians in the building above. The three talk about why Eren came to Marley, and likewise why Reiner came to the Walls. The two draw similarities between each other, Eren stating he understands him now.
Willy draws his speech to a conclusion with an emotional plea to the ambassadors of other nations, for the world to unite in the fight against Paradis. As Willy declares war on Paradis, inside of the basement, Eren transforms into the Attack Titan, emerging from the building behind Willy and crushing the stage. This attack sends debris flying into the crowd, and eviscerates Tybur's form.