<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> <P> Combating the Titans is the military, which is divided into three branches . Foremost in the story is the Survey Corps (調査 兵団, Chōsa Heidan), which goes out into Titan territory to try to reclaim the land . The Survey Corps are heavily derided in society because of their apparently senseless high casualty rate and little sense of progress . The second and largest branch is the Garrison Regiment (駐屯 兵団, Chūton Heidan), which guards the walls and the civilian populace . The third branch is the Military Police Brigade (憲兵 団, Kenpeidan), who guards the royal family and live relatively relaxed lives, although this eventually results in fraud, corruption, and political subterfuge . The soldiers use a tethering system called Vertical Maneuvering Equipment (立体 機動 装置, Rittai Kidō Sōchi) acting as a grappling system, allowing them to jump onto (and swing from) walls, trees, or nearby buildings to attack Titans with dual swords . However, despite it being the soldiers' primary line of both offense and defense against the Titans, it is useless in open and flat terrain like fields . </P> <P> It is later revealed that the Titans were created when Ymir Fritz found the "source of all organic life" and became the Founding Titan where she had the ability to create and control the Titans . When Ymir Fritz died as a side effect of having the Titan ability for 13 years, her soul was split into the 9 Titans where their abilities can be inherited by anyone once the previous wielder is dead . These Titans consist of the Founding Titan, the Attack Titan, the Colossus Titan, the Armored Titan, the Female Titan, the Beast Titan, the Jaw Titan, the Cart Titan, and the War Hammer Titan . The 145th King that wielded the Founding Titan's power fled to the island of Paradis where he used the countless Colossus Titans to make the walls and erased the memories of the Eldians he brought with him so that they didn't know anything about the outside world . </P> <P> The story of Attack on Titan revolves around the adventures of Eren Yeager, Mikasa Ackerman, and their childhood friend Armin Arlert . After the wall which protects their hometown of Shinganshina is breached by the Colossal Titan leading the other Titans to enter, Eren watches in horror as a smiling Titan eats his mother . Vowing to kill all the Titans, Eren enlists in the military, along with his friends . </P>

The story behind the titans in attack on titan
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