Mercy

Mercy is the first chapter of the eighth volume of Shingeki no Kyojin and the 32nd chapter overall.

Summary
With Annie's secret out, Armin fires off his flare gun to signal the hiding scouts to apprehend her. They manage to grab her before she is able to bite her hand and transform. Unknown to them however, she has a blade hidden in her ring which she uses in the struggle. Mikasa, noticing the ring just in time, grabs Armin and Eren and pulls them to safety. As they round the corner, Annie explodes into her titan form and sends the mangled bodies of her would-be captors flying down the stairs.

Reacting quickly again, Mikasa drags her friends further into the tunnel as the titan arm of Annie reaches in after them. Starting to second guess his plan, Armin begins to lose confidence. Mikasa reminds him of the situation and gets him to focus on what they should do next. Agreeing, Armin tells them to follow through with plan B and to meet the next group in the tunnel to get it underway. As they approach the group 3, they barely manage to give the order when Annie stomps through the street above and into the tunnel, crushing the scouts underfoot. Armin, seeing the risk Annie took with collapsing the tunnel, realizes her desperation to capture Eren. They are trapped. If they move forward, Annie will see them through the hole she created and if they stay still, she could stomp down again and kill them. With no other choice, Eren decides to transform and fight Annie himself. He grabs his hand and bites down, but nothing happens. Armin tells him to focus on his goal, but it's no use. Mikasa wonders if Eren doubts that it's actually Annie and reminds him of all of their comrades that she killed.

Eren thinks back to a couple of days earlier. He and Levi sit at a table together and after light conversation, Eren apologizes again for the decision he made. Levi tells him that there was no way they could have predicted that outcome. Soon after, Commander Irvin walks in with Mikasa, Armin and few other scouts. He tells the two that they know who the female titan is and states their plan to capture her. In order to draw her out, they will hand Eren over. Though the plan is risky, it's the only move they have left. Irvin tells Eren that it was Armin who discovered her identity. She was the one who killed the titans used for research and she is a member of the 104th Trainees Squad. The information triggers a memory of fighting the her in the Forest of Giant Trees and then of hand-to-hand combat training with Annie. Shocked, Eren can't believe that Armin would accuse Annie. Armin solemnly gives his reasons. She knew what Eren's face looked like, as she was actively looking at peoples faces before she killed them and she reacted to his nickname of "Death-Seeker"; a name no one outside of their class would know. He states further that, when everyones 3-D maneuver gear was inspected after the titan specimens were killed, Annie turned in Marco's instead of her own. Levi, seemingly unconvinced, asks for more proof. Mikasa says that their faces look similar, causing Eren to question the decision even more. In the end, Armin says that if they don't act on this information, Eren will just become a sacrifice for the capital. Still in disbelief, Mikasa tell Eren to think back to his fight with her and to note the similiarities causing Eren to finally concede.

Still trapped in the tunnel, Armin comes up with a plan. He and Mikasa will both leave the tunnel at the same time and head in different directions. This will cause Annie to have to choose one or the other and give Eren and the other survivor their chance to escape. When Eren asks how they can do this, Mikasa gives him the answer that he gave her the day he saved her from the kidnappers, "because the world is a cruel place". Eren, worried for his friends as they get in position, answers her back with, "it sure is". Now having the motivation he needs, he bites down on his hand and bursts through the tunnel to the surface. Catching Annie by surprise, he delivers an uppercut that sends her flying through the air.