Attack on Titan, Volume 12

Erwin and the Survey Corps desperately mount a rescue operation to take Eren back from the Colossus Titan and Armored Titan. But without the numbers to form up properly outside the walls, how can the humans catch up before they're all slaughtered? Just whose side is Ymir on? And will Eren ever see his friends again?
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 the human race has hidden in a giant, three-walled city. People believe their 100-metre-high walls will protect them from the Titans, but the sudden appearance of an immense Titan is about to change everything.