Armin Arlert (アルミン・アルレルト Arumin Arureruto?) is the best friend of Eren Yeager and a member of the 104th Training Corps. In Mikasa's dream, he appeared as a young boy who attempts to escape the Walls using an airplane that he and Eren made.
Armin has a round face, blond hair that is cut in the style of a bob cut. He wears the standard 104th Training Corps uniform. In Mikasa's dream, he is shown as a small boy wearing a light-button-up shirt and long light pants.
Armin cares deeply for his friends, crying over their deaths. Armin dreamed of traveling the world beyond the walls. In Mikasa's dream, he enjoys making and working on different things such as a butterfly container and a prototype airplane his parents made. He is a foolish boy, believing that he was able to make a working airplane. After Eren's death, he faults himself for telling Eren about the outside world.
In Mikasa's dream, Armin spends many days playing with Eren Yeager from day to night. The two boys bonded over their desire to travel outside the Walls. Armin told Eren about his parents' death. His parents had tried to build an airplane to go outside the Walls but failed and died. Armin showed Eren a prototype airplane that his parents had worked on. Together the two made improvements to the airplane. They soon completed the airplane and decided to fly over the Walls at night. During the time that they worked on the airplane, Armin gifted Eren a butterfly container that he had made.
On the night of their planned trip, Armin runs in the rain to deliver a message to Mikasa. He falls to the ground as he tells her about Eren's death. He tells her it is his fault for telling Eren about the outside world, and says the airplane failed to take off and that Eren saved him by pushing him out of the plane before crashing into the Wall. Armin starts to apologize to Mikasa.
- Eren Yeager - Eren was Armin's childhood friend. Sometimes they played with each other from morning to night. They shared the same dream to travel the world outside of the Walls. Armin gifted Eren a butterfly container that he made.