<P> The spin - off light novel series Before the Fall began in December 2011 and has received a manga adaptation . Two additional light novel series and four additional spin - off manga series have also been created . An anime television adaptation is being produced by Wit Studio and Production I.G, aired in Japan on MBS . The first season aired between April and September 2013, the second season aired between April and June 2017, and a third season is scheduled to be released in April 2018 . 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, with another game developed by Spike Chunsoft for the Nintendo 3DS . A two - part live - action film adaptation, Attack on Titan and Attack on Titan: End of the World, and a live - action web - series were released in 2015 . An anime adaptation of the Junior High spin - off manga, produced by Production I.G, began airing in October 2015 . Attack on Titan and all five spin - off manga are published in North America by Kodansha Comics USA, while the three novel series are published by Vertical . The anime has been licensed by Funimation for North America, by Manga Entertainment for the UK, and by Madman Entertainment for Australasia . </P> <P> Attack on Titan has become a commercial success . As of April 2017, the manga has 66 million copies in print . The release of the anime also saw a boost in the series' popularity, with it having received widespread critical acclaim for its atmosphere and story . Although it also gained fame in neighboring Asian countries, the series' themes have been a subject of controversy . </P> <P> Over 100 years before the beginning of the story on an alternate world, giant human - shaped creatures called Titans (巨人, Kyojin) suddenly appeared and nearly wiped out humanity, devouring them without remorse or reason . What remains of humanity now resides within three enormous curtain walls: the outermost is Wall Maria (ウォール ・ マリア, Wōru Maria); the middle wall is Wall Rose (ウォール ・ ローゼ, Wōru Rōze, sometimes pronounced like rosé) and the innermost is Wall Sheena (ウォール ・ シーナ, Wōru Shīna, alt . "Wall Sina"). Inside these walls, humanity has lived in uneasy peace for one hundred years; many people growing up without ever having seen a Titan . This all changes when one day, a giant 60 - meter (200 ft) - tall Colossus Titan mysteriously appears after a strike of lightning and breaches the outer wall of the Shiganshina district, a town at Wall Maria, allowing the smaller Titans to invade the district . An Armored Titan smashes clean through the gate in Wall Maria, forcing humankind to abandon the land between Wall Maria and Wall Rose, evacuating the remaining population into the inner districts . The sudden influx of population causes turmoil and famine . </P> <P> The Titans are giant humanoid figures ranging between 3--15 meters (10--50 ft) tall and are usually masculine in body structure but lack reproductive organs . Although they do not appear to need food, they instinctively attack and eat humans on sight; it is mentioned that they derive their energy from sunlight . Furthermore, the Titans also do not have a proper digestive tract; once they have eaten their fill of human prey, Titans will vomit large, slimy balls, derisively referred to as "hairballs". Finally, their skin is tough and difficult to penetrate, and they regenerate quickly from injuries, save for a weak spot at the nape of their neck . </P>

Who build the walls in attack on titan
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