Season 1

A century of peace within the Walls comes to an end when the outer part of Wall Maria is breached by the massive Colossal Titan. The breach allows other Titans to flood into the Shiganshina District. Things worsen when the hardy Armored Titan breaches the inner wall, causing humanity to completely withdraw behind Wall Rose.

Following the loss of his mother and home to the Titans during this incident, Eren Yeager, his adopted sister, Mikasa Ackerman, and their friend Armin Arlert retreat with other refugees behind Wall Rose. Eventually, they decide to join the army. Eren also has a strange dream in which his father, Grisha, forcibly injects an unknown serum into him. Grisha also warns Eren not to forget the key to their basement, which contains a secret known only to Grisha.

Five years later, Eren and his friends graduate. As part of the top ten graduates, they are able to join the Military Police that guard the interior and are furthest from the action. However, Eren wishes to join the frontlines as a Scout instead. Mikasa and Armin also decide to become Scouts. Their first day as graduates coincides with the second appearance of the Colossal Titan, who breaches Wall Rose and leaves the Trost District vulnerable to attack.

The following battle to defend Trost results in Eren being consumed by a Titan. Things look grim for the humans, but an unusual Titan with combat skills and knowledge of the Titans’ weak points unexpectedly comes to their aid. To the surprise of the other graduates, they witness Eren emerging from the Titan’s body after it collapses; the limbs that Eren had lost when he was eaten have also been regenerated. Later, the military forms a plan in which Eren transforms into a Titan again to close the breach in Wall Rose. After temporarily losing control, Eren manages to seal the breach with a boulder.

In the aftermath of the Battle of Trost, the Military Police wish to have Eren killed, while the Scouts’ commander, Erwin Smith, wants to use him to retake Wall Maria. In the end, Eren is allowed to join the Scout Regiment where he is assigned to the squad of Levi Ackerman, the man regarded to be humanity’s strongest soldier. Eren is brought to an abandoned castle for training and assists researcher Hange Zoë in her tests. Hange has two captured Titans in her possession, but they are found dead the next day. The killer is deduced to be a human capable of using omni-directional mobility gear.

The Scouts, now including a number of graduates from Eren’s cadet batch, head to Saganshina for an operation, only to be waylaid by the unexpected appearance of an intelligent Female Titan who is after Eren. Armin has a close encounter with the Female Titan, but it spares his life after seeing his face. Armin theorizes that the Female Titan is a Titan shifter like Eren.

Although the Female Titan is eventually restrained, the person inside it manages to escape before they can be extracted by the Scouts. Erwin suspects that the Titan shifter is hiding amongst the Scouts. The Female Titan’s second attempt at securing Eren is foiled by Levi and Mikasa, but she escapes again and leaves behind many casualties, including most of Levi’s Special Operations Squad, in her wake.

Due to the failed operation, the Scouts are summoned to the Capital and ordered to hand over Eren. Annie Leonhart, a cadet from Eren’s batch who now serves in the Military Police, is asked by Armin to assist them with Eren’s escape. However, the real plan is to determine if Annie is the Female Titan, which turns out to be the case. The Scouts fail to stop her from transforming, but Eren manages to defeat her in his Titan form after a fierce battle. Annie crystalizes herself to avoid interrogation.

Following Eren and Annie’s clash, the Capital rescinds its order to have Eren handed to them and allows the Scouts to have custody of Annie. A post-credits scene shows a portion of Wall Sina that was damaged by the fight. A part of the wall falls off to reveal the face of a Titan inside it.