Attack on Titan (進撃の巨人 Shingeki no Kyojin , lit. "Advancing Giants") is a Japanese manga series written and illustrated by Hajime Isayama. The story centers around the lives of Eren Yeager, his adoptive sister Mikasa Ackerman, and their friend Armin Arlert, who live in a world where the remnants of the human population live inside cities surrounded by enormous walls due to the sudden appearance of the Titans, gigantic humanoid creatures who devour humans seemingly without reason. Their lives are changed forever after the appearance of a colossal Titan brings about the destruction of their home town and the death of Eren's mother, spurring them to enter the army to battle the Titans themselves.
An anime television series debuted on April 6, 2013, on MBS.[Note 1] A live action film adaptation is also in production. Four video game adaptations developed by Nitroplus staffers in collaboration with Production I.G were announced to be released as bonus content for the third and sixth volumes of the Blu-ray Disc release of the anime.
The manga series has become a commercial success, selling over 20 million volumes as of mid 2013. The release of the anime also saw a boost in the series' popularity with several writers critically acclaiming for its atmosphere and story. Although it also gained fame in neighboring Asian countries, the series's themes have been a subject of controversy.
One hundred years prior to the beginning of the story, giant humanoid creatures called Titans (巨人 Kyojin ) have forced humanity to retreat into a system of concentric Walls (ウォール Wōru )known as Wall Maria (ウォール・マリア Wōru Maria , outermost), Wall Rosé (ウォール・ローゼ Wōru Rōze , middle), and Wall Sina (ウォール・シーナ Wōru Shīna , innermost). Inside these walls, humanity lived in peace for one hundred years, but in the beginning of the story, a sudden attack by a gigantic sixty-meter Titan and a smaller Titan covered in armor plates causes the outermost wall to be breached, forcing mankind to abandon the land between Wall Maria and Wall Rosé, which leads to famine and turmoil.
Little is known about the Titans, giant creatures that are usually between 3-15 meters tall with a few exceptions. The Titans instinctively attack and devour ordinary humans on sight. However, they apparently do not need to feed to survive, as they do not prey on other animals, even with the long absence of humans, and can survive by absorbing sunlight. They have hard skin and regenerative abilities, and can only be killed by a deep incision on the base of the neck. This weakness led to the development of the Vertical Maneuvering Equipment (立体機動装置 Rittai Kidō Sōchi ), allowing humans to navigate quickly in a three-dimensional space to access the Titans' weak point. Although it allows great mobility to a skilled user, it carries a large risk of overtaxing the muscles, requiring special physical conditioning and a sense of balance to master it.
The series follows the story of Eren Yeager, his adopted sister Mikasa Ackerman, and their friend Armin Arlert. After the outermost Wall is breached by Titans, including the 60-meter tall skinless Colossus Titan and the abnormally intelligent Armored Titan, and his mother dying in the resulting destruction, Eren vows revenge against the Titans and later enlists in the military, accompanied by Mikasa and Armin. Years later during his first battle against the Titans, Eren discovers that he has the ability to transform into a Titan at will. Seen as a threat to mankind by some, and as a ray of hope by others, Eren joins his companions in a desperate fight to protect what remains of their society while looking for answers to the mysteries surrounding the Titans, the Walls, and his own existence as well.