Hange Zoë

Hanji Zoe (ハンジ・ゾエ) is a Squad Leader from the Scouting Legion. She conducts research on Titans and, as such, is deeply interested in Eren Jaeger, who can turn into a Titan.

Personality
Hanji is very passionate about her work. She can be seen as very hyper and very active, often diving into her work without thought for personal safety and documenting the experiences. However, her lectures are very boring and astute soldiers quietly leave the room before she begins one.

Hanji is often excited by Titans and is always eager to experiment with them, coming off as extremely emotional regarding titans. For example, she cried at the amount of pain she was giving a titan during one of her experiments.

She explained her strange actions to Eren as a way to see titans from a different perspective and learn new insights that would normally be overlooked from the traditional views of rage.

However, Hanji still cares deeply for humanity and her comrades as seen  when she confronted Pastor Nick for his coverup of the Wall. When he refused to talk, she personally grabbed him and held him over the side of Wall Sina, explaining that lives were lost because of him and his religious faction and that she holds him in utter contempt.

Current Plot
Hanji Zoe is introduced when she takes Eren to his military hearing in front of the leaders of the human military. She is present with the rest of the Scouting Legion as Rivaille beats up Eren and checks on his condition after the tribunal is over, noting that the gap where Eren lost his tooth earlier is fast disappearing.

All of her experiments with captured Titans "Sonny" and "Bean" turned up no vital evidence which is why Hanji is so excited to work with Eren.

Later, when Eren and the Special Operations Squad are at the former Scouting Legion HQ, she begins to prep Eren on her experiments, but ends up talking until morning when she is interrupted. Hanji was about to talk about the curious precedent involving Ilse Langner when it was discovered that Bean and Sonny were murdered.

Although devastated by the loss of her test subjects, Hanji moves forward with her experiments on Eren. When it turns out Eren cannot turn into a titan at will, she is a little disheartened. However, seeing Eren's titan hand later on got her very excited, unexpectedly breaking the tension between Eren and the Special Operations Squad.

She discovered that Eren's titan powers are only awakened when he has a clear objective in mind, such as defending against the cannonball. She also theorized that this switch must have a good reason as well as being connected to the titan's nature.

She stops Keiji from continuing to try and open the crystal Annie Leonhardt put around herself to avoid capture. She directs her men to take it away quickly when she notices the titan within Wall Shina.

Before she can do react, Pastor Nick hurries to her and tells her to stop sunlight from hitting the titan's face. After this, she tries to question the Pastor about what they had just seen, but he roughly tells her she doe not need to know anything about it and even threatens compensations for damages done to his church.

Furious at his attitude, Hanji pulls Nick over the edge of the Wall and threatens him to tell her why there are titans inside the Wall. She comes to the conclusion that the his religion has been so opposed to Wall modifications because of what they know is inside the Wall. She explains that the people of the Scouting Legion sacrifice their lives hoping that one day, it will mean something. Thus, they have a right to know what they saw and why it is there.

However, Pastor Nick is willing to die to maintain his secrets and Hanji decides to let him live. He finally tells Hanji and the other members of the Scouting Legion about Historia knowing more about the walls having titans in them. She went under an assumed name after she was caught in the middle of her relatives dispute and will tell them more about it, if she choses to.

After Hanji's squad rescue the Scouts trapped at Castle Utgard, Hanji tells everyone that its time to go. The Scouts begin to leave. After seeing Mikasa try and kill Reiner and Berthold, Hanji proceed to attack the colossal titan and hold up pretty well till it exerts burning gas.

Trivia

 * Hanji's identity is ambiguous in the Japanese. It's suspected to be male, but Isayama's not saying; his exact words in an interview were, "そのキャラ（ハンジ）の性別は明言しない方がよさそうだ" ("looks like I'm better off not making it clear").
 * EDIT: The above was mentioned by Isayama in March 2011. In Volume 5 of the manga, which was released in August 2011, Hanji Zoe is depicted in civilian clothing, with a decently noticable chest and a skirt. Her official feminine anime character design also reflects her gender; thus, Hanji Zoe is undoubtedly female.