The story of Attack on Titan centers around the adventures of Eren Yeager, his adopted sister Mikasa Ackerman, and their friend Armin Arlert. After the wall which protects their hometown of Shinganshina is breached by Titans, Eren watches in horror as one of them eats his mother. Vowing to kill all Titans, Eren enlists in the military along with his friends.
Five years later, the three cadet graduates are positioned in Trost District, one of the border towns jutting out of Wall Rose, when the Titans attack again. In the ensuing battle, Eren is eaten by one of the Titans before Armin's eyes. However, a Titan later appears that begins fighting the other ones instead of harming humans; the Titan is revealed to be Eren, who has somehow developed the ability to transform into one. Though he is seen as a threat by some, he helps the military take back Trost. After being placed on trial for being a danger to the humans, he is taken in by the Survey Corps' Special Operations Squad, led by Captain Levi.
In an expedition to Shinganshina, the Scouts are attacked by a Female Titan who attempts to capture Eren. Although the Scouts are able to briefly capture the Female Titan, she breaks free and devastates Levi's squad, forcing the expedition to retreat. Armin determines that the Female Titan is Annie, one of the cadets who taught Eren to fight, and devises a plan to capture her at Stohess.
Others are discovered to be able to transform into Titans, with several seeking Eren for some unknown purpose which they refer to as the coordinate. The Walls themselves seem to be hiding something from the populace as shown by the fact that Titans make up the walls. As is the royal family and the Military Police who also need Eren to keep him from causing an uprising, as well as his friendKrista Lenz, who is really named Historia and is next in line to the throne.
The Survey Corps, seeing the turmoil and decadence caused by the current royal family, the Reiss Family, decide to mount a rebellion and use Eren and Historia as bait. The rebellion is successful but Rod Reiss, the current king, captures Eren and Historia. He reveals that a Titan was the one who created the walls 100 years ago and it modified most people's memories. A few bloodlines were spared from the modification but their children did not gain these details. Eventually only the person who held the Titan's power knew anything of the new world. Through a series of circumstances the power has come to Eren, who Rod says Historia must consume to retake the power.
