Armin Arlert grew up in Shiganshina District with childhood friends Eren Yeager and Mikasa Ackerman, often relying on them for protection against bullying. His grandfather showed him a forbidden book about the outside world, sparking a lifelong fascination with oceans, ice fields, and lands beyond the walls. After the Titan breach of Wall Maria, he became a refugee and joined the 104th Training Corps alongside Eren and Mikasa. Though his physical combat skills were low, his exceptional strategic intellect earned him recognition. Armin is defined by a combination of deep curiosity, empathy, and self-doubt, along with a morally complex worldview that rejects absolute definitions of good and evil. His tactical brilliance proved crucial in battles such as sealing the breach in Trost District, identifying Annie Leonhart as the Female Titan, and devising the plan to recapture Shiganshina. During that fight, he sacrificed himself as a decoy against the Colossal Titan, suffering near-fatal burns. Captain Levi chose to revive him with Titan serum instead of Commander Erwin Smith, leading Armin to inherit the Colossal Titan by consuming Bertholdt Hoover. He later became the 15th commander of the Survey Corps after Hange Zoë. Armin grapples with survivor’s guilt and the burden of leadership, especially as he opposes Eren’s genocidal Rumbling. He forges an alliance with former enemies, uses his Colossal Titan powers strategically, and continues to advocate for diplomacy and understanding even in the midst of war. His relationships with Eren, Mikasa, and Annie Leonhart—whom he visits regularly while she is crystallized—remain central to his journey.