Armin Arlert is the 15th and current commander of the Survey Corps, named so by Hange Zoë before their death. He is also a childhood friend of Eren Yeager and Mikasa Ackerman, and one of the two deuteragonists of the series. Although he appears to be among the physically weakest of the 104th Training Corps, his intelligence and strategic genius makes him an invaluable asset, especially when paired with Hange. After the battle of Shiganshina District, he took the power of the Titans from Bertolt Hoover and came in possession of the Colossus Titan.
Armin has a boyish face, with large hazel eyes and a small pointed nose which is always distinctly a bit red. His blond hair is styled in a long undercut with bangs over his entire forehead. Armin has noticeable defined eyebrows and sideburns, indicating his age. His frame is, as it has always been, relatively small and lacking in muscle but not the definition. During the attack on Liberio, Armin is seen wearing a standard cloak for hiding purposes before he transformed. He is noticeably a bit taller and has his hair cut shorter.
Even when he was young, the naturally curious Armin had a deep fascination with the world beyond the Walls. As a child, he found and studied an illegal book about the outside world that was owned by his grandfather. He told Eren Yeager, his best friend, about the book and the information that was contained in it. Armin was branded a heretic by other children for his unusual interest in the outside world, and was thus frequently picked on. Too timid to defend himself, Armin would often rely on his friends Eren and Mikasa Ackerman to protect him from local bullies. This, coupled with his frail physique, was a source of much shame for Armin, leading him to have poor self-esteem and to believe that he was a burden to others. Because of this, Armin has always been very eager to prove his worth. As a child, he hoped that one day he would be able to consider himself a true equal to his friends.
Appearance: Armin has a boyish face, with large hazel eyes and a small pointed nose which is always distinctly a bit red. His blond hair is styled in a long undercut with bangs over his entire forehead.
Personality: Even when he was young, the naturally curious Armin had a deep fascination with the world beyond the Walls. As a child, he found and studied an illegal book about the outside world that was owned by his grandfather.
History: Armin originally lived in the Shiganshina District of Wall Maria. After his parents were executed for attempting to escape the Walls, he was left to live with his grandfather.
Armin Arlert in the story: In the year 845, Armin would once again find himself cornered by bullies who mock him for his deep curiosity for the outside world. Refusing to fight back, Armin would need to be rescued by the timely appearance of Eren and Mikasa. Later, he and his two friends settle by the riverbank, where Eren broods over his desire to join the Survey Corps.
Source: Attack on Titan Wiki, available under CC BY-SA 3.0.