Armin Arlert was born in Shiganshina District within Wall Maria and orphaned young after his parents died trying to explore the outside world via hot air balloon. Raised by his grandfather, he discovered an illegal book detailing oceans, deserts, and other wonders beyond the Walls, sparking an intense curiosity about the outside realm. This passion made him a target for bullies, and he relied on childhood friends Eren Yeager and Mikasa Ackerman for protection and support. Despite his physical frailty and self-doubt, Armin joined the military alongside them. His physical limitations contrasted with a sharp strategic mind, which became vital to the Survey Corps. He devised critical operations including the reclaiming of Trost District, the capture of the Female Titan, and a trap for the Colossus Titan during the battle of Shiganshina. That sacrifice left him mortally burned. Captain Levi chose to save Armin with Titan serum instead of reviving Commander Erwin Smith, and Armin inherited the Colossus Titan by consuming Bertolt Hoover—an act that filled him with survivor’s guilt. He later became the 15th Commander of the Survey Corps after Hange Zoë’s death. During the Liberio raid, he wielded the Colossus Titan’s devastating power. When Eren initiated the genocidal Rumbling, Armin opposed him, believing mass eradication betrayed their shared dream of exploring the world. Imprisoned by Yeagerists, he escaped to form an alliance of former enemies to stop Eren. In the final battle, he was devoured by an Okapi Titan and transported to the Paths dimension, where he persuaded Zeke Jaeger to relinquish his life, halting the Rumbling. In a private conversation with Eren, he mourned their fractured friendship. After Eren’s death, Armin claimed credit for killing him to protect Mikasa and became a peace ambassador, navigating diplomacy between Paradis and foreign nations. Physically, he has a slender build, blond hair, and a wide-eyed gaze; after inheriting the Colossus Titan, he gained subtle height and cropped hair. As the Colossus Titan, his form is skeletal and steam-scorched with a gaping throat and hollow eyes. His relationships are defined by his childhood bond with Eren and Mikasa, a tentative connection with Annie Leonhart that grew during her imprisonment, and the respect of senior officers like Levi and Hange.