In a three-part OVA based on the 'Shingeki no Kyojin: Lost Girls' spinoff novel, Annie Leonhart faces a secret mission that must remain undisclosed. Seeking help from her friend Hitch Dreyse, Annie must first solve Hitch's unsolved missing person case involving Carly Stratmann, a woman from a wealthy family. Racing against time in the dangerous Stohess District, Annie unearths more mysteries than answers, including the presence of a forbidden drug and hidden truths about Carly's father. Meanwhile, Mikasa Ackerman, haunted by worry for Eren Yeager, delves into her memories, reliving moments of friendship, despair, and a haunting reality where some events seem destined to unfold despite her efforts to change them.