Attack on Titan Volume 0

Chapter 0 is the official dub title for the draft story written by Hajime Isayama which would later evolve into Attack on Titan. The draft story had a very different setting, but certain aspects of the Attack on Titan world were already in place. It was released alongside the DVD version of the first volume of the anime on July 17, 2013.

Setting
Being an early draft of the series, most things about the world were quite different from the current story. People used to build their cities inside Forest of Giant Trees, instead of Walls, because it was noted by humans that Titans didn't harm wildlife because they were pure-hearted beings, and consequently, wouldn't harm the trees. These cities seems to be built using wood and all the buildings seems built by a similar patron. There are advanced technology like an alarm system.

The Military appears to only have two divisions, although only one is ever mentioned. The Vanguard seems to have later evolved into the Survey Corps, as they are the ones actively fighting Titans outside of the cities. The Vanguard uniform consist of battle pants and a light colored jacket that covers the user's arms and hip. The jacket has printed on the back the symbol of the army.

Titans
The Titans themselves were part of a human extermination project led by scientists and religious groups 100 years before the story. These groups had also created an event called The global crisis to memory. Titans were said to be vastly superior to any living being. Not only did they have the ability of regeneration and immortality, they were also able to shape shift into the forms of humans.

Instead of being in the nape of their necks, their weak spot was located in a place inside their bodies which varied from Titan to Titan. This weak spot, called nucleus, had the form of a sphere surrounded by little spikes. Attacking this weak point was fatal.

Unlike in Attack on Titan, all Titans have a very similar appearance. They have humanoid bodies with a thin frame and lack external sexual organs. Their exact height is unknown, but they are big enough to hold an average human with one hand. They lack hair, pupils, and their teeth are exposed.

Titan Shifters were also present, and were shown to have already infiltrated the Military. Somewhat similarly to their current counterparts, killing them was impossible while they were in their human form, and attempting this would trigger their transformation. Only hitting their weak spots in Titan form would cause their death.

Weaponry
Though somewhat similar in looks to 3DMG, instead of dual sharp blades and the the ability to fight in 3D space, humans were only equipped with two flaming katana blades that were capable of shooting fire. The fire can be shot straight or in a circular motion. They are fired by using the friction of a small rock, similar to a lighter. It's also shown that soldiers are able to perform super-high jumps to attack Titans.

Story
The story begins in a somewhat desert looking area, similar to the desert area in the Attack on Titan back story. While a group of Vanguard soldiers prepare to fight a Titan, a brief summary is given about the origins of Titans and their abilities. One by one the soldiers are eaten, their bodies lay strewn across the ground. One last soldier approaches the Titan from behind while it's eating the other soldiers; hoping to kill the Titan and save whoever may still be alive. As he leaps to make his attack the Titan turns around just in time.

Back at the city a soldier named Murakumo makes his way back to the barracks. Upon his arrival he sees Tsubaki, a young girl who wishes to be trained by him. She begins to beg when he refuses her request, but a soldier notices her wooden blades and asks if she wants to join the Vanguard Corps. Murakumo begins to think about how she's just like her father, and how she's just as eager as he was when his parents died. He gives her a task: he'll teach her if she practices blade swinging 100 times everyday. She's excited, but asks whether he joined the Vanguard out of revenge. He passionately replies that he joined the Vanguard to protect his allies, he tells Tsubaki not to forget that. Their conversation catches the attention of another soldier who just watches as Murakumo leaves.

Murakumo is working in another part of town, when all of a sudden he's surrounded by armed soldiers. They demand that he take off his equipment and surrender. They believe he may be a Titan and have just been given the "go ahead" to take him in. It comes to Murakumo's attention that they sent humanity's greatest military strength to apprehend him. Due to fear, the soldiers are quick to lay blame on him. And despite repeatedly demanding he take off his equipment, he instead unsheathes his sword and cuts a soldier in half. It turns out the soldier he cut was actually a Titan masquerading as a human. A man who was eaten 10 years ago, who turns out to be Murakumo's father. The Titan shows it's true form and is much bigger than they expected. To their dismay a couple more soldiers turn out to be Titans as well. While the evacuation alarm is set off, the smaller Titans begin eating the much larger Titan.

While a soldier watches in shock, Murakumo prepares to confront the Titans. The soldier thinks he's crazy and suggests that they retreat with everyone else. He believes that since the Titans have broken into the city there will be no way for them to reclaim it. He gets more frantic as he goes on, saying "MANKIND... CANNOT WIN AGAINST... THE TITANS! WE'RE DOOMED!!" Murakumo refuses to give up hope, but before he can make a decision; Tsubaki, armed with kitchen knives, calls out to the Titans. Now in their sights a Titan lunges for her, but she's saved just in time by Murakumo. He tells her she's done well and to leave the fight to him. The frantic soldier watches him fight the Titans, he begins wondering why Murakumo fights and why he's still groveling on the roof. Filled with rage the soldier joins the fight. Murakumo finds the Titan's weak spot, and the soldier finishes him off. Believing the Titan to be dead they prematurely begin to celebrate. Before they have time to react the Titan is already up with half of the soldier in it's mouth. Murakumo races toward the Titan but is quickly grabbed. The whole time Tsubaki watches, thinking it's all a bad dream. The Titan bites a portion of Murakumo and turns it's attention back toward Tsubaki.

Murakumo manages to use his remaining arm to cut the Titan's hand off. And to Tsubaki's shock he transforms into a Titan. The Titan continues to make it's way toward Tsubaki, but is grabbed and thrown a long distance away. Meanwhile, Murakumo thinks back to when he transformed into a Titan for the second time. He goes on a rampage killing the other Titans, until one attacks him from behind. In his frenzy to stop the Titan he ends up revealing his weak spot, but also manages to reveal the Titan's weak spot as well. The Titan turns out to be a bit quicker and bites into his weak spot. Realizing he's about to die, he bites into the Titan's weak spot as well. As he melts away the Titan remains, and Tsubaki prepares to fight for her life, but before it can move it melts away as well.

Some time later Tsubaki is at a grave, made by the townspeople, for Murakumo. While she cries about losing her master, a brief summary is given on the ability to control Titan powers. Refusing to succumb to sadness, she gets up and begins the last task Murakumo gave her: 100 blade swings everyday.

Trivia

 * Unlike current Titans, all Titans in Chapter 0 looked alike. With the only noticeable difference being size and weight.
 * Unlike current Titans, they don't need to eat a Titan Shifter to turn back into a human. They seem to be able to take the form of any human they eat. Though it doesn't appear that they gain the memories of those they eat.