Hannes was a unit captain of the Garrison. He was also a close friend to the Yeager family and was responsible for saving Mikasa and Eren's lives from a Titan.
Hannes was a tall, well-built man with short blond hair, a thin dark mustache. He wore the typical uniform of the Garrison Regiment along with a v-neck shirt underneath.
Hannes was a very kind, good-natured man, but he always drank irresponsibly. Although somewhat cowardly, he was determined to die if it meant freeing Eren from his captors. He was greatly ashamed of his lack of courage five years ago, and waited to encounter the Titan who killed Eren's mother, Carla Yeager, again, in order to slay it and make up for his past mistakes.
Appearance: Hannes was a tall, well-built man with short blond hair, a thin dark mustache. He wore the typical uniform of the Garrison Regiment along with a v-neck shirt underneath.
Personality: Hannes was a very kind, good-natured man, but he always drank irresponsibly. Although somewhat cowardly, he was determined to die if it meant freeing Eren from his captors.
History: When Keith Shadis found a civilian beyond Wall Maria, the man was imprisoned for leaving the Walls without permission, and Hannes was stationed at his jail cell to watch him. Drunk while on duty, Hannes was perplexed that anyone besides the Survey Corps would be "stupid" enough to leave the Walls, suggesting instead that the man may have left the Walls while intoxicated, explaining his memory loss.
Hannes in the story: While on duty, Hannes and his companions keep themselves entertained by drinking and playing card games. Their fun is interrupted by Eren Yeager, who criticizes them for not taking their job seriously and demands to know what they would do if Wall Maria was breached by the Titans while they were drunk. Hannes nonchalantly assures the boy that the Walls will never be breached and argues that Eren should be happy that the Garrison has nothing to do, as the day that they have their work cut out for them will be the day that Titans really do break in and threaten the peace of the Walls.
Source: Attack on Titan Wiki, available under CC BY-SA 3.0.