Cleaver

Ōnata (大鉈) is the 1st chapter of the 21st volume and the 83rd chapter overall of the Attack on Titan manga, written and illustrated by Hajime Isayama.

Overview
As Eren mourns for his deceased friend Armin, he is confronted by Zeke. Zeke recognizes Eren, attempting to tell him about his father Grisha brainwashing him, but is interrupted by the arrival of Levi Ackerman. Before he leaves, however, Zeke promises to rescue Eren. As Eren prepares to give Levi his gas tanks, he hears Armin cough.

Hange attempts to interrogate a captive Reiner, but when they are unable to get any meaningful information from him, Jean suggests taking his Titan powers from him. Unconvinced that the Titan serum should be used yet, Hange tells Mikasa to check on Eren and Armin, and to alert her if Reiner should be killed. However, shortly afterwards Zeke and the Quadrupedal Titan appear and rescue Reiner.

As Eren frantically tries to keep Armin alive, he begs Levi to save Armin's life with the Titan serum. Levi agrees, but is stopped by the arrival of the surviving Survey Corps recruit who is carrying Erwin's near-lifeless body. Seeing that Erwin is still alive, Levi announces that he has changed his mind, and will instead use the Serum to save Erwin. The others object to this and turn on Levi while Zeke watches from atop Wall Maria with Reiner.

Summary
Several years ago in Shiganshina District, Armin sits against a wall crying while bullies walk away laughing. Eren, peering from around the corner of a building, asks Armin why he is allowing the bullies to treat him that way. Armin says that he has not lost, since he is not running away. Stepping forward, Eren asks him what his name is.

In the midst of the fight for Shiganshina, Eren looks down upon the burned body of Armin. Realizing the horrific situation, he falls to his knees, admitting that he expected the outcome. Acknowledging Armin's hand in their success in defeating Bertolt, he wonders why Armin never runs away from his fights. While he mourns, Zeke riding upon the quadrupedal Titan falls into the district, having climbed over Wall Maria. The Titan leaps towards Eren and Bertolt, and Eren grabs Bertolt holding a blade to his neck. Ordering Zeke to stay away, Eren notices the signs of Titan shifting on Zeke's eyes, concluding that he must be the Beast Titan. Zeke asks Eren if he is indeed Eren Yeager, and rather than answering Eren begins to cut into Bertolt's throat. Before Eren can finish Bertolt off, Zeke remarks that Eren looks nothing like his father. Zeke claims that he understands Eren and wants to help, saying that both he and Eren are victims of Grisha, who Zeke claims has brainwashed Eren in some way. Eren looks to Zeke in shock, noticing a striking resemblance between Zeke and Grisha.

Before their conversation can continue, Zeke notices Captain Levi standing atop Wall Maria, drenched in the blood of slain Titans. As Levi descends from the wall, Zeke abandons Bertolt and promises that he will return to rescue Eren some day. Levi lands on the rooftop beside Eren as Zeke flees, and Levi asks for Eren's gas and blades so that he can pursue him. While Eren prepares to do so, he notices Armin coughing.

Elsewhere in the district, Hange questions Reiner, limbless and blindfolded after his defeat, about the contents of a metal case he was reaching for. While Mikasa treats Jean's wounds, Reiner tells Hange that the case contains a letter from Ymir that must be given to Historia. Hange tells him that they will check the contents of the letter before delivering it. Drawing her blade, she asks Reiner if he is willing to answer her questions. When he declines, she prepares to kill him. However, Jean urges her to wait, reminding her that they may be able to steal his Titan powers instead.

Before the expedition, Commander Erwin had informed the entirety of the Survey Corps of the nature of the Titan serum possessed by Levi. Erwin declares that their primary objectives to defeat the intelligent Titans and reclaim Wall Maria have not changed, and that the Titan serum will be prioritized for those who are most grievously injured. He emphasizes that only one dose of the serum is in their possession.

Hange tells Jean that she does not believe the requirements of the serum's use have been met yet. Jean notes that Hange's hesitation is unlike her normal attitude. Hange orders Mikasa to check on Eren and Armin, telling her to fire a signal flare in case of an emergency so that she can know when to kill Reiner. As Mikasa leaves, Hange tells Jean that the decision was her own, and that his words were the data that she based the decision off of. She wonders who the serum should be given to, since Sasha is not fatally wounded and there may be someone else more heavily injured.

As Mikasa arrives with Eren and Levi, Eren frantically tells Armin to keep breathing. Turning to Levi, he asks for the serum so that Armin can be revived by eating Bertolt. Levi agrees, and Mikasa fires off her signal flare.

As Jean notices Mikasa's flare, Zeke arrives on his Titan to take Reiner. As the Titan lunges at Hange, Jean quickly pulls her out of the way while Zeke and his Titan mount take Reiner away. Connie attempts to pursue them, but Hange orders him to stay since his gas is low and he could be defeated easily if something were to go wrong. Jean punches the ground in frustration, but Hange assures him that the decision was her own. Hange informs the others that they are to regroup with Levi and the others.

As Levi is handing the serum over to Eren, the surviving recruit from Erwin's charge arrives, carrying a fatally wounded Erwin on his back. Seeing Erwin's condition, Levi hesitates in giving up the serum. He checks for life, and confirms that Erwin is indeed alive. While the others look on with worry, Levi declares that he is going to give the serum to Erwin. Eren steps forward with tears in his eyes, reminding Levi of his choice to save Armin. Levi tells him that he plans to save the one who will save humanity. While the recruit looks on in confusion, Mikasa draws a blade, stepping forward with tears in her eyes while Levi gives her a look of understanding.

From atop Wall Maria, Zeke looks down at the ruins of the city, letting Reiner know how lucky he has become.

Trivia

 * The title of the chapter refers to the Japanese phrase "wield the hatchet (大鉈を振るう)", a figure of speech referring to a moment of taking great strides.