Jean Kirstein is a graduate of the 104th Training Corps, among whom he ranked 6th best. Jean hails from Wall Rose's Trost District, and joined the military with hopes of obtaining a peaceful life as part of the Military Police Brigade, but would later find himself joining the Survey Corps. He served as a commanding officer in the Survey Corps, leading a squad during the Raid on Liberio.
Jean is a young man with spiky, gray hair shaved into an undercut style, with the shaved portion being black. He has small, intense brown eyes, and is said to have the same vicious look in them as Eren does. Jean is of average height and muscular build, and has a scowl similar to Eren's but is said to have a long face (a "horse face"). He is often seen wearing the typical uniform of the Survey Corps worn with an olive-gray button-up shirt. After overthrowing the government, his hair appears slightly longer than before.
Jean has a blunt personality. He holds no restraint when it comes to speaking his mind, even when he knows it would not be wise to do so or when it could spark conflict. Jean is also pragmatic: he has a strong aversion to exposing himself to dangerous situations, and has openly admitted his desire to join the Military Police is due to wanting an easy and safe life.
Appearance: Jean is a young man with spiky, gray hair shaved into an undercut style, with the shaved portion being black. He has small, intense brown eyes, and is said to have the same vicious look in them as Eren does.
Personality: Jean has a blunt personality. He holds no restraint when it comes to speaking his mind, even when he knows it would not be wise to do so or when it could spark conflict.
Jean Kirstein in the story: After coming of age, Jean enlists into the military, joining the 104th Training Corps. On the day of his enlistment, Jean confidently admits his desire of joining the Military Police and receives a headbutt from Keith Shadis for his troubles. That night, Jean overhears Eren Yeager talking about his desire to join the Survey Corps and criticizes him for the decision, but apologizes after seeing that his words have upset Eren.
Abilities: Jean is highly adept at using vertical maneuvering equipment, being able to maneuver well even on open terrain, which is considered extremely difficult and not many people can do so. He has also shown his capability in being able to attack and slay Titans efficiently even without his proper equipment and can successfully maneuver around them in order to directly attack their nape or simply avoid them.
Source: Attack on Titan Wiki, available under CC BY-SA 3.0.