Jean Kirstein hails from Trost District in Wall Rose. He enlisted in the 104th Cadet Corps driven by a singular ambition: joining the Military Police Brigade for a secure life within the inner walls, openly prioritizing comfort and safety over the dangers of frontline combat. This pragmatic focus on self-preservation sparked frequent clashes with the idealistic Eren Jaeger, who championed the Scout Regiment. Ranking 6th overall in cadet training, Jean demonstrated notable skill with omni-directional mobility gear. A competitive drive pushed him to outperform Eren, though he often neglected disciplines not critical for a top-ten graduation. His early demeanor revealed a hot-headed cynicism about humanity's odds against the Titans. His close friend Marco Bodt saw potential in him, arguing Jean's self-awareness and pragmatic judgment made him command material, despite Jean's own reluctance. The Battle of Trost District proved pivotal. Facing the Titan invasion, Jean initially panicked, despairing that the attack destroyed his Military Police aspirations. Stranded with other cadets lacking gas, he reluctantly rallied survivors alongside Mikasa to reach the supply depot. Forced to abandon comrades as Titan bait, he wrestled with profound guilt over exploiting their deaths for tactical survival. This trauma reshaped his perspective, a process intensified by discovering Marco’s corpse—a loss that later ignited his resolve to uncover the truth behind his friend's demise. Jean's development included vulnerable moments. During a cadet cooking competition judged by Commander Dot Pyxis, his fierce desire to win nearly led him to steal meat. He abandoned the plan upon receiving a homemade omelet from his mother; reconciling with her publicly, he won the contest with this humble dish. By the battle's end, Jean abandoned his Military Police goal. Though eligible, he chose the Scout Regiment to honor Marco and confront the Titan threat directly. His leadership during the crisis—assessing risks, making brutal life-or-death calls, and fostering cohesion among terrified soldiers—cemented his reputation as a capable, if reluctant, tactical commander.