Alpha Squad

Called the Seiei-han, or elite squad, in Japanese, the unit exists for exactly one operation. After trainee Armin Arlert proposes sealing the Trost breach with a boulder, Pixis pulls together Rico Brzenska, Mitabi Jarnach, and Ian Dietrich, hands Ian overall command, and leaves the operational details, including the authority to call everything off, entirely to his judgment.

The squad's job is escort duty under nightmare conditions: shield the transformed Eren from every Titan pouring into the city while he hauls a boulder to the broken gate. Taking the shortest route, the plan collapses almost immediately when Eren loses control of his Titan form, swings at Mikasa Ackerman, and knocks himself out. Rico fires a red flare to signal failure and, backed by Mitabi, argues for abandoning the "failed human weapon" and retreating up the Wall. Ian refuses. In a heated standoff he insists that a human who can become a Titan is a card humanity cannot afford to fold, and his conviction pulls the squad back into position even as Titans mass around them.

Ian Dietrich leads the operation and dies in its final stretch. Rico Brzenska survives to fire the yellow flare confirming success, grateful that the deaths bought something real. Mitabi Jarnach perishes with his entire squad while luring two Titans away from Eren. Eren Yeager and Mikasa Ackerman fill out the roster from the 104th, and Armin Arlert, though never formally assigned, reaches the group mid-fight and talks Eren's dormant Titan back to its senses, making the sealed gate possible. The survivors are saved at the end by the arrival of the Survey Corps, with Levi Ackerman cutting down two Titans closing on the group.