Annie Leonhart was trained by her father from a young age until the time came for her to partake in an attack on the Walls on behalf of Marley. Before she set out, Annie's father apologized to her and assured her that regardless of what the world thinks of her, she will always have her father on her side. He remained in Marley awaiting his daughter's return.
After the Warriors' attack on Shiganshina District, Annie Leonhart joins the 104th Training Corps under secret orders. When the time comes for graduation, she participates in the battle of Trost District. After graduating from her Training Corps, she joins the Military Police Brigade while her Warrior comrades Reiner Braun and Bertolt Hoover join with the Survey Corps.
Annie infiltrates the 57th Expedition Outside the Walls, devastating the mission as the Female Titan. A few days later, she is caught in Stohess District but crystallizes herself in a hardened skin shell, falling into stasis to prevent interrogation.
Shortly before the Battle of Shiganshina District, Bertolt remembers back to the Battle of Trost District, where Reiner had pressured Annie to take off Marco Bott's vertical maneuvering equipment, to prove that she and her father were different from the "evil race" within the Walls
Before the curtain's rise at Willy Tybur's production in Liberio, Mr. Leonhart speaks with Karina Braun, the latter praising Annie for having devoted her life to Marley. Mr. Leonhart refuses this, adamantly stating that she is alive, because she had promised to come home.