Annie Leonhart ranked fourth in the 104th Training Corps and joined the Military Police Brigade. Her early life involved intense combat training under her adoptive father, who aimed to secure privilege by making her a Warrior for Marley. This brutal regimen left her emotionally detached, struggling to value human life, and culminated in her attacking her father, leaving him permanently crippled. Chosen as a Warrior candidate, she inherited the Female Titan power. Alongside fellow Warriors Reiner Braun, Bertolt Hoover, and Marcel Galliard, Annie participated in a mission destroying a rival nation to prove the Warriors' effectiveness. In 845, she infiltrated Paradis Island to retrieve the Founding Titan. During Wall Maria's fall, she used her Female Titan form to gather Titans breaching Shiganshina District, causing significant civilian casualties. Personally reserved and emotionally distant, Annie avoided forming attachments. She openly stated her motivation for joining the Military Police was survival, not idealism. Despite her aloofness, she displayed complex moral awareness, showing reluctance to kill former comrades like Armin Arlelt and visible distress during Marco Bodt's death. Her fighting style emphasized efficiency and precision, excelling in hand-to-hand combat and tactical analysis. She possessed the unique ability to crystallize parts of her Titan body for offense or defense. During the events covered in "Attack on Titan Part 1: Guren no Yumiya," Annie operated undercover. She discreetly eliminated captured Titans researched by Hange Zoë to hinder Paradis Island's understanding of Titan physiology. Suspected by the Survey Corps, her identity led to a confrontation where she transformed to escape. After battling Eren Jaeger in his Titan form and intervention by Mikasa Ackerman, Annie crystallized herself into an indestructible shell to avoid interrogation, entering a comatose state. Following approximately four years of confinement underground, Annie escaped during a conflict involving the Military, Yeagerists, and Marleyan forces. This period marked a shift; she became more willing to collaborate with former enemies like Armin and Mikasa to oppose Eren Yeager's genocidal actions. She openly acknowledged her past atrocities, expressing self-loathing and a sense of being irredeemable, yet also conveyed gratitude for Armin's visits during her imprisonment.