Several hundred years ago, humans were nearly exterminated by titans. Titans are typically several stories tall, seem to have no intelligence, devour human beings and, worst of all, seem to do it for the pleasure rather than as a food source. A small percentage of humanity survived by walling themselves in a city protected by extremely high walls, even taller than the biggest of titans. 
Flash forward to the present and the city has not seen a titan in over 100 years. Teenage boy Eren and his foster sister Mikasa witness something horrific as the city walls are destroyed by a colossal titan that appears out of thin air. As the smaller titans flood the city, the two kids watch in horror as their mother is eaten alive. Eren vows that he will murder every single titan and take revenge for all of mankind. 
(Source: MangaHelpers)

In this post-apocalyptic sci-fi story, humanity has been devastated by the bizarre, giant humanoids known as the Titans. Little is known about where they came from or why they are bent on consuming mankind. Seemingly unintelligent, they have roamed the world for years, killing everyone they see. For the past century, what's left of man has hidden in a giant, three-walled city. People believe their 50-meter-high walls will protect them from the Titans, but the sudden appearance of an immense Titan is about to change everything.
 
(Source: Kodansha USA)
 
Note: Includes 2 extra chapters.

A recompilation of the anime series. The new films will feature new dubbing and a 5.1ch remaster with returning voice cast members. The second film will cover 14 through 25.

Oluo no Chichi