Attack on Titan

=== Setting ===

Attack on Titan centers on a civilization within three circular walls. According to local belief, it is the last surviving vestige of human civilization. Its inhabitants, known as Eldians, have been led to believe that, over one hundred years ago, humanity was driven to the brink of extinction by the emergence of humanoid giants called Titans, which attack and eat humans on sight. The last remnants of humanity retreated behind three concentric walls and enjoyed roughly a century of peace. Within the walls, residents are strongly discouraged from venturing outside. To combat Titans, the country's military employs Vertical Maneuvering Equipment (VME), also known as Omni-Directional Maneuvering Gear (ODM gear), a set of waist-mounted grappling hooks and gas-powered propulsion that enables mobility in three dimensions. Swords made of ultrahard steel are used in conjunction with the gear, and later, rocket launcher–like weapons known as Thunder Spears are developed by commander Hange Zoë.
Titans are classified into several types. Pure Titans are the weakest and most common, whose predictable behavior makes them easier to kill. Abnormal Titans are Pure Titans whose behavior is less predictable, making them harder to face in combat. The Nine Titans, also known as Titan Shifters, are the Attack, Colossal, Armored, Female, Beast, Jaw, Cart, War Hammer, and Founding Titans. They are the strongest Titans; each is able to shift back and forth between human and Titan form to access their Titan's abilities. Many Titan shifters possess the ability to harden certain parts of their bodies at will, typically in order to make them nearly impenetrable, or to strengthen their blows during combat.
Pure Titans are created by injecting Eldians with Titan spinal fluid. If a Pure Titan consumes a human who possesses one of the Nine Titans, that Eldian will revert to human form and gain that Shifter's powers, whereupon they are cursed to live only 13 more years. If the powers are not inherited by another Eldian before the holder's death, they are passed to an Eldian baby born shortly thereafter, regardless of distance or blood relations. As the story progresses, the true nature of the Titans and the existence of civilization outside the walls are revealed.

Plot

Eren Yeager is a boy who lives in the town of Shiganshina, located on the outermost of three circular walls which protect their inhabitants from Titans. In the year 845, the first wall, Wall Maria, is breached by two new types of Titans, the Colossal Titan and the Armored Titan. During the incident, Eren's mother is eaten by a Smiling Titan while Eren escapes. He swears revenge on all Titans and enlists in the military along with his childhood friends Mikasa Ackerman and Armin Arlert.
Five years after Shiganshina's fall, the Colossal Titan attacks the city of Trost, located in the second innermost wall, Wall Rose. Eren helps to successfully defend the city after he discovers a mysterious ability to turn himself into a sentient Attack Titan. Additionally, he regains memories of his father Grisha Yeager giving him this ability shortly after the fall of Wall Maria, and telling him that the truth about their world can be found in their basement in Shiganshina. These events draw the attention of the Survey Corps and their commander, Erwin Smith, who intend to use his power to reclaim Wall Maria and reach the Yeagers' basement. Eren, Mikasa, and Armin are transferred to the Special Operations Squad, under the care of Levi Ackerman and Hange Zoë. During an expedition into the forest between the walls, Eren and his companions encounter a sentient Female Titan, who is later revealed to be their fellow military comrade Annie Leonhart. With help from his friends, Eren fights and defeats Annie, who encases herself in crystal and is put in custody. After the fight, it is discovered that there are Titans lying dormant within the walls, known as Wall Titans.
Shortly thereafter, Pure Titans mysteriously appear within Wall Rose with no evidence of how they got in, accompanied by the sentient Beast Titan. Ymir, one of the new Survey Corps graduates, reveals that she can transform into the sentient Jaw Titan, while Ymir's close friend Krista Lenz reveals herself as Historia Reiss, a member of the royal family. Two other members of the Survey Corps, Reiner Braun and Bertholt Hoover, reveal themselves as the Armored and Colossal Titan respectively. They attempt to kidnap Eren and Ymir, but fail. In the ensuing battle, Eren discovers another power within himself called "the Coordinate", that allows him to control other Titans, which he uses to kill the Smiling Titan and send a horde of Pure Titans to attack Reiner and Bertholt. This forces the two to escape, and Ymir willingly flees with them, offering herself as a sacrifice to prevent Historia from being targeted by the enemy. In the aftermath of these events, it is determined that the Pure Titans who suddenly appeared within Wall Rose were the inhabitants of various villages within Wall Rose, who had in some way been transformed into Titans. This leads the characters to the conclusion that all Pure Titans are, in fact, transformed human beings.
Eren and his friends join Levi Squad while the Survey Corps is targeted by the Military Police led by Kenny Ackerman, Levi's uncle. In the occasion, they discover that by transforming into a Pure Titan via a serum made of Titan spinal fluid and eating another Titan shifter, a person can inherit its abilities, and that Historia and her father, Rod Reiss, are the only surviving members of the royal bloodline. Rod kidnaps Eren because he is in possession of the Founding Titan, obtained by his father Grisha upon eating Frieda Reiss (Historia's half-sister), and by Eren through eating his father. Rod tries to convince Historia to allow herself to be transformed into a Titan, so she can eat Eren and regain the Founder's power. After Historia refuses and breaks Rod's vial of spinal fluid, Rod attempts to consume the serum himself, transforming into a monstrously large Abnormal Titan and mortally wounding Kenny; he is then killed by Historia (with the help of the Survey Corps), who is thereafter declared Queen.
Having resolved the political unrest, the Survey Corps lead a successful operation to recapture Shiganshina, fighting the Beast, Colossal, Armored, and Cart Titans but suffering massive casualties, wherein Erwin dies in a suicide run against the Beast Titan, and Armin gains ownership of the Colossal Titan when Levi injects him with a serum given by Kenny, causing Armin to eat Bertholt. Eren and his companions return to his childhood home, where they discover the truth of their world: they are actually Eldians, sworn enemies of the conquering Marleyans who were enclosed within the walls after the original King Karl Fritz fled from the war. They are not the last humans as they were told, but rather an enclosed sect of Eldians on an isolated island called Paradis. Because they are "Subjects of Ymir" who can be turned into Titans by being injected with Titan spinal fluid, the Eldians continue to be oppressed by Marley. In the year after the battle of Shiganshina, the Survey Corps kill all of the remaining Pure Titans on the island.

Three years later, the Survey Corps launch an attack against the Marleyan capital of Liberio, orchestrated by Eren and his half-brother Zeke, who is the owner of the Beast Titan. Eren kills Willy Tybur, an Eldian who (along with his family) had been controlling Marley from the shadows and gains ownership of the War Hammer Titan after eating its previous owner, Willy's sister Lara. Eren is imprisoned for acting against orders but escapes with a faction of extremist Paradis soldiers called the Yeagerists. Zeke is kept in Levi's custody but manages to escape, severely injuring but not killing him. Marley's air fleet, led by Reiner, launch an invasion of Paradis, and chaos breaks out in the ensuing battle. Eren and Zeke reunite, which leads them to the Paths—a series of atemporal gateways connecting all Eldians through time and space. There, they meet the consciousness of Ymir Fritz—the original Titan—whose tortured past led to her imprisonment within the Paths for thousands of years. Zeke attempts to convince Ymir to fulfill his wish to stop the Subjects of Ymir from reproducing via mass sterilization. Eren, however, convinces Ymir to use her power to bring about the Rumbling—unleashing thousands of Wall Titans kept within Paradis's walls and leading them on a genocidal march to kill everyone outside the island.
The Survey Corps ally with the remaining Marleyan forces, including Reiner and a newly freed Annie, to stop Eren. They defeat the Yeagerists before confronting him, though many are killed, including Hange. Levi kills Zeke and Mikasa kills Eren, which causes the mysterious creature that is the source of all Titans' powers to die and the power of the Titans to vanish, reverting all Titans to human form, and stripping the Titan Shifters of their powers, thereby freeing all Eldians from the curse. His death also releases memory blocks that he put on his friends, revealing that what transpired was part of Eren's plan to spare twenty percent of humanity, with Armin, Levi, Mikasa, and the others being recognized as heroes in the eyes of the world for killing him and stopping the Rumbling. Three years later, as Paradis and the rest of the world rebuilds, Armin and his allies begin peace negotiations led by Queen Historia. Mikasa buries Eren underneath a tree on a hill near Shiganshina District. The tree grows over time to resemble the one where the organism that granted Ymir her Titan power lived. An unspecified amount of time after Mikasa's death from old age, a modernized Shiganshina is reduced to rubble in a war. The series ends with a boy and his dog approaching the tree, which has now become surrounded by wilderness.