|What do you see? Who do you think the enemy is?|
|— Erwin Smith questions Eren|
Now in the custody of the Survey Corps, Eren is taken to their headquarters under the supervision of Squad Levi. Captain Levi quickly puts his soldiers to work on cleaning the fortress. Eren briefly talks with squadmate Petra Ral, who tells him about Levi's shady past. Later at night, Squad Levi discusses the upcoming expedition and their need to learn about Eren's power of the Titans. Squad Leader Hange then joins them to discuss the progress of her Titan experiments. Eren asks about these Titan experiments, causing the others to quickly leave before Hange begins a long discussion on her research.
Hange discusses her findings involving her research on Sonny and Bean, the Titans that were captured from Trost. Eren discovers that Hange has a strange sympathy for the Titans she experiments on, and asks her about it. She explains that her research has suggested that the true nature of the Titans may be more than what humans would believe, causing her to see things from a different angle. Eren asks for even more information about Hange's experiments, leading her to talk until dawn.
That morning, a soldier interrupts their discussion to alert Hange of Sonny and Bean's sudden deaths. Outside, many Survey Corps soldiers are gathered around the Titans' steaming remains while Hange cries in dismay. As Eren looks at the scene, Erwin suddenly appears behind him, asking him who he thinks the real enemy is. Eren cannot answer him, and Erwin apologizes before leaving.
Now in the custody of the Survey Corps, Eren is escorted to their former headquarters. Oluo Bozado tries to intimidate Eren, but ends up biting his tongue. Later at the fortress, Petra Ral scolds him and tells him he got what he deserved. Arriving at the headquarters, Eren takes a look at the people around him. Levi's squad, also known as the Special Operations Squad, are in charge of keeping an eye on him and will have to put him down if he gets out of control.
Seeing the state of the place, Captain Levi orders everyone to start cleaning it up. A short while afterward, Eren approaches Levi and asks where his room is. Levi tell him the conditions on which he was released to their custody; he is told he must stay in the basement. Levi says that if he was to turn into a Titan in his sleep, it would be easier to contain him in the basement. He then leaves to check on the other rooms. Petra tries to comfort Eren. He says that Levi is not what he expected, obeying the orders he is given rather than playing the rogue. Petra says that he used to be the kind of person that did whatever he wanted, living a life of crime in the Underground until Erwin Smith convinced him to join the Survey Corps. Moments later, Levi returns to tell Eren to clean the other room over again.
Sitting around a table later that night, the team discusses the plans for a large scale operation to the outer lands. Another member of the team asks Eren what it feels like to become a Titan. Eren begins to explain that he bites down on his hand, but stops once he realizes that he has no idea where that knowledge came from. Soon after, Hange walks in and asks Eren if he can help with their experiments. While Eren is under the care of the Survey Corps, he does not have control of his schedule and defers to Levi. After getting permission, Eren asks what kind of experiments he will have to help with. After the rest of the squad leaves the room in a hurry, Hange explains the nature of their studies of Titans.
Their first experiment was an attempt at communication. Unable to make any headway, they moved on the effect of light deprivation. One Titan showed an immediate change, while the other was active for three hours before slowing down. The next experiment was to find out if the Titans experienced any pain. This experiment seemed to affect Hange more than the Titans. The larger Titan Bean, showed a slight reaction to having its eye gouged out. While the smaller Titan, Sonny, showed no reaction to having a spear in his heart at all, besides trying to eat Hange mid-experiment.
Before Hange can continue, Eren asks why she can be so cheerful around Titans despite their horrid nature. Hange explains that she lost many friends to the Titans and used to use her hatred against them, until one day she kicked the head of a 10m Titan and noticed that it was much lighter than it should have been. She explains that Titans should not even be capable of bipedal movement, but it becomes possible since their bodies are much lighter than they should be. She then brings up the fact that all of Eren's Titan bodies materialized out of thin air. She concludes by saying that what humans can see and the true nature of the Titans' existence are totally different things. Because of this, she chooses to look at the Titans from a different angle despite the apparent absurdity.
Intrigued, Eren asks for more information, which Hange all too happily gives. Having stayed up all night talking about their experiments, Hange admits that everything she discussed was probably old news to Eren. She begins to speak of the strange situation experienced by Ilse Langnar when they are interrupted by a soldier who rushes in and tells them that the Titans they were using have been killed. They rush outside and find smoldering lumps where the Titans used to be. Levi says that the Military Police Brigade will take care of the investigation. Commander Erwin suddenly appears behind Eren and asks him who he thinks the enemy is. Seeing that he is confused, Erwin apologizes for asking such a strange question and walks away, leaving Eren wondering what he meant.