Armin Arlert

Large hazel eyes dominate Armin's boyish face, set off by a small pointed nose that always shows a touch of red. As a teen he wears his blond hair in a bob and stands short for his age, his slight frame carrying definition but little muscle. By 854 he has grown taller, restyled the hair into a long undercut with bangs across the forehead, and gained visible sideburns and heavier brows. He moves through the story in the 104th trainee uniform, the classic Survey Corps jacket and green expedition cape, and finally the Corps' redesigned black gear for the Marley raid.

His sixty-meter Colossus Titan is a skinless horror: spindly arms hanging past its knees, thickly muscled legs on stubby feet built to balance its height, an exposed rib cage, and a face of bare bone with no nose, sunken mournful eyes, and a naked windpipe at the throat. Unlike Bertolt's version it possesses lips, and it lacks outer ears. The Pure Titan form he briefly held echoed his human self, blond shoulder-length hair on a scrawny, lipless, black-eyed body.

Curiosity defines Armin from childhood. A forbidden book of his grandfather's, filled with salt seas and deserts, plants the dream of the outside world that he passes on to Eren, and the same interest gets him branded a heretic and beaten by other children. Too timid to fight back, dependent on Eren and Mikasa for protection, he grows up ashamed of his frailty and convinced he is a burden, an insecurity that leaves him desperate to prove his worth. Trost teaches him that his mind is a weapon in its own right, and his confidence builds from there, though he never fully learns to value his own life; he volunteers for death with unsettling ease, whether surrendering his horse, his gas, or his body to the Colossus Titan's steam.

He is analytical to the bone, a planner and improviser whose creative thinking makes even senior officers listen, yet leadership in the spotlight leaves him anxious and prone to freezing. He idolizes leaders like Erwin Smith who can discard their own humanity for a goal, and he preaches logic over feeling, but his empathy keeps betraying the doctrine: he vomits with guilt after shooting a woman to save Jean and emerges from his rampage at Liberio in tears. Believing morality is relative, he hates being called a good person and will build ruthless, underhanded plans that shock everyone except Eren and Mikasa, who always knew he had it in him.

Born in Shiganshina and raised largely by his grandfather after losing his parents, Armin befriends a young Eren Yeager, the first boy to ask why he never runs from his bullies. In 845 the two friends and Mikasa watch the Colossus Titan breach Wall Maria; Armin's quick word to Hannes saves Eren and Mikasa without their knowing. Orphaned fully when the government's land reclamation drive consumes its conscripts, he enlists at twelve. In Trost his first battle destroys his squad, and Eren is devoured pulling Armin from a Titan's mouth. Out of that despair Armin engineers the retaking of the supply depot, argues the military out of executing the newly revealed Titan-shifter Eren, and drafts the boulder plan that seals the gate, humanity's first victory.

His deductions expose every infiltrator in the 104th. Spared twice by the Female Titan, he reasons out that she is Annie Leonhart and baits the trap in Stohess that ends in her crystal; evidence he assembles helps unmask Reiner and Bertolt. At the battle of Shiganshina he locates Reiner hiding inside the Wall, and when the Colossus Titan turns the district to ash, he spends his own life as the decoy, clinging to the Titan's teeth while its steam chars him so Eren can strike the nape. Levi, holding the last Titan serum, chooses the dying Armin over the dying Erwin; as a Pure Titan Armin devours Bertolt and wakes healed, carrying the Colossus Titan and its shortened thirteen-year lifespan. A year later he finally stands in the ocean he read about as a boy, while Eren stares across it at the enemy shore.

The dream curdles in Marley. Armin sinks the naval fleet at Liberio with his explosive transformation, then weeps at what he has become, and Sasha's death deepens the rift with Eren, who beats him bloody at Niccolo's restaurant and calls him Bertolt's puppet. Armin still deduces the truth, that Eren is deceiving Zeke and Yelena, and he plays along with the Yeagerists until the Rumbling reveals a plan he cannot accept: the extermination of everyone outside the island. He joins the alliance of old friends and old enemies, survives three bullets at the harbor, and receives command of the Survey Corps from a dying Hange at Odiha. In the final battle a Titan swallows him; inside Paths he wins over Zeke with a leaf and a memory of racing his friends up a hill, waking the past inheritors who turn the tide. Freed, he transforms to grapple Eren's colossal form and pins its head so Mikasa can deliver the killing stroke. His erased memories of Eren's farewell return with the seashell and the truth: his friend chose to become the world's enemy so the survivors could be its saviors. Facing Marleyan guns, Armin introduces himself as Eren Yeager's killer, and three years later he sails for Paradis as a peace ambassador, still certain some part of the world remains undiscovered.