Armin Arlert grew up in Shiganshina District behind Wall Maria, where his grandfather’s forbidden book about the world beyond the Walls sparked a deep curiosity and dream of exploration. His parents died attempting to leave the Walls by hot air balloon, and he was raised by his grandfather until the fall of Wall Maria, when his grandfather also perished. Bullied for his unorthodox ideas, Armin found protection and friendship in Eren Yeager and Mikasa Ackerman. Physically frail but exceptionally intelligent, he joined the military and graduated from the 104th Training Corps. Though overshadowed by his comrades’ combat skills, his tactical brilliance proved indispensable in key battles, including unmasking Titan shifters and engineering the capture of Bertolt Hoover. During the battle of Shiganshina, he suffered near-fatal burns but was revived with Titan serum, inheriting the power of the Colossus Titan from Bertolt. This rebirth came with survivor’s guilt, as the choice to save him over Commander Erwin Smith weighed heavily on him. As the Colossus Titan, his form was towering and skinless with elongated limbs. Armin’s appearance changed over time from a delicate blond youth to a composed adult with shorter hair. He succeeded Hange Zoë as the 15th commander of the Survey Corps. When Eren initiated the apocalyptic Rumbling, Armin rallied both Paradis and Marleyan allies against the genocide, entered the Paths dimension to convince Zeke Yeager, and confronted Eren, understanding but rejecting his methods. After the conflict, he became a peace ambassador, working to end cycles of hatred between nations. Throughout his journey, Armin balanced empathy with cold pragmatism, often questioning the moral costs of his strategies, such as civilian casualties during the Liberio raid. His evolution from a timid, doubting youth to a resolute leader embodied the struggle between idealism and harsh necessity.