|I want to join the Scouts...and slaughter every Titan I can!|
|— Eren states his intentions|
Primal Desire: The Struggle for Trost, Part 9 (原初的欲求 ―トロスト区攻防戦⑨― Genshoteki Yokkyū -Torosuto-ku Kōbōsen (9)-?) is the 13th episode of the 1st season and the 13th episode overall of the Attack on Titan anime, produced by Wit Studio and Production I.G.
After the skirmishes between the cadets and the Titans come to a close, the soldiers of Trost see Eren carrying the boulder to the breach and defend him with their lives. Once the breach is sealed, the Scout Regiment arrives to assist in clearing out the remaining Titans.
After the battle, the cadets assist in clearing out the corpses, and Jean finds Marco's body. Some time later, Eren awakens in a cell supervised by Commander Erwin and Captain Levi, who accepts him into the Scouts.
The elite soldiers continue to lead the struggle to defend Eren. However, Rico's squad, excluding Rico herself, is completely wiped out in the battle, leaving only her and one female soldier. As they are forced to retreat to the boulder's location, they witness the arrival of more Titans heading their way.
At this time, Jean is attempting to take a dead soldier's omni-directional mobility gear as his own one broke, while being watched from top of the Wall by Annie, Conny and now Marco as well. Having trouble with their gear, Jean is approached by a Titan. Luckily, Marco manages to make it to Jean's location in time to distract the Titan long enough for Jean to acquire the gear and escape. Conny and Annie also rush in to help, and when Jean finds himself having difficulties controlling the gear, Conny distracts the Titan pursuing him in order to give Jean time to readjust. Jean finally manages to control the gear just to be approached by another Titan, however, he ends up being ultimately saved by Annie and all four of them successfully escape to the top of the Wall. Suddenly, they hear loud footsteps and much to their surprise, they witness Eren in his Titan form walking towards the gate, carrying the huge boulder.
The elite team, along with Mikasa, also watches in surprise. They are approached by Armin who tells them that Eren won and is trying to do his job now. He notes that if he manages to reach the gate, they will win. Seeing this as their ultimate chance, Ian orders the soldiers to protect Eren, even if it costs them their lives. Jean, Annie, Conny and Marco also descend from top of the Wall with the intention to support Eren. Afterward, Ian tells Armin and Mikasa, to go directly to Eren, and then goes into action himself, but suddenly stops, surprised to see Mitabi and his squad approaching the Titans on ground. Armin claims that staying on ground is suicide, but Ian states that it is the only way they have left to keep the Titans distracted from Eren and heads down to successfully distract a Titan, creating a path for Eren.
As Eren keeps walking towards the hole, he notices Armin and Mikasa and becomes worried that they may get eaten by Titans. The soldiers continue luring the Titans, however, some of them are caught in the battle, including Mitabi, who gets crushed by a Titan's hand while distracted by the death of one of his comrades. Eren then recalls Armin questioning his motive for going outside. He states to himself that when people are born, they are free and people who deny that, no matter how strong they are, do not matter. Believing that seeing the world outside would make one the freest person, he keeps walking forward, determined to fight, no matter how cruel the world is.
Meanwhile, the soldiers keep getting eaten by the Titans with less than a handful of them remaining. Mikasa and Armin witness Ian Dietrich sacrificing himself by grabbing a soldier out of a Titan's mouth, which in turn grabs Ian and bites his head off. As one more Titan stands in Eren's way, Rico charges forward, cutting through its eye, with Mikasa finishing the job. Finally reaching the hole, Eren, while being encouraged by Armin, drops the boulder, successfully blocking the breach in Trost.
With tears in her eyes, a relieved Rico says that the soldiers did not die in vain and shoots a yellow signal flare as a message that the mission has been accomplished. Seeing this, Dot Pyxis immediately orders to send reinforcements and rescue the elite team.
With more Titans approaching, Rico exclaims that they have to climb the Wall as soon as possible, but Mikasa rushes to Eren who is still partially attached to the Titan's body. Rico quickly decides that they have to cut him off, and she herself does the job. However, at that moment, two Titans reach them and as they are about to attack, they are slain by a mysterious soldier. But then, Eren spots the "Wings of Freedom," the symbol of the Scout Regiment on the soldier's back. As the soldier approaches them, their savior turns out to be Captain Levi. Standing atop of the killed Titan, Levi looks at Eren and friends, and questions the situation.
After that, both Garrison, and Scout Regiment keep eliminating the Titans trapped inside Trost. Thanks to the cannons and Scout Regiment's prowess, the area of Trost becomes free of Titans after a whole day of fighting. Not only that, but two Titans are also captured alive. However, while mankind finally manages to win against the Titans, the price paid in exchange is far too high as a lot of soldiers have died or are injured.
Having to deal with the aftermath of the battle, Jean is then seen going through the corpses. Much to his shock, he then witnesses a corpse of Marco. Unable to believe this, he questions what happened. However, he is then approached by a combat medic who asks Jean for the deceased's name. After hearing that they are still collecting corpses in order to avoid an epidemic and knowing the names is helpful, Jean tells her Marco's name and his position as a soldier. Elsewhere, Sasha witnesses a lot of corpses as well. Questioning this, she is told by a soldier, much to her disbelief, that they are corpses that were thrown up by a Titan. At the same time, Annie is also looking at a corpse of a soldier, apologizing to her. Reiner, however, tells her that an apology will not fix it so they should just put them to rest.
At an unknown place, Eren suddenly wakes up, and is being interrogated by Erwin Smith and Levi of the Scout Regiment. After being told that he is in an underground jail cell, and in the custody of the Military Police, Eren notices that Erwin is holding a key to the basement of his former house. Stating that he will give it back to Eren later, Erwin tries to confirm whether the basement holds the secrets of Titans, to which Eren replies that it is what his father said. Not trusting him, Levi states that it is convenient for Eren to have amnesia while his dad is missing, but Erwin insists that Eren has no reason to lie. When Erwin asks him what he wants to do later on, Eren sadistically replies that he wants to kill all the Titans he can. This catches Levi's interest, as he walks forward, and says that he will take care of Eren, not because he trusts him, but because he can kill him if Eren betrays them. He then tells Eren that he will accept his application to the Scout Regiment.
Currently Publicly Available Information
A History of Battles Against the Titans
The oldest available records say the Titans appeared 107 years ago. They devoured most of humanity.
Humanity retaliated with cannons, but they were useless in the face of the Titans' regenerative ability.