Attack on Titan GN Volume 20

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 humanity. For the past century, what's left of mankind has hidden in a giant, three-walled city. Now, a young boy consumed with rage displays a strange ability: The power to transform into a Titan! Is this the lucky break humanity needs to survive?