Milieus Zeremski was of average height with bluish-gray eyes and ash blond hair. He wore the typical uniform of a member of the 104th Cadet Corps.
Milieus seemed shy and cautious; he warned Eren when he was running off to avenge Thomas Wagner for fear of his safety and inexperience. However, he showed bravery when charging in with his squad to save his comrade.
During the Struggle for Trost, Milieus is assigned to a middle guard squad in Trost District. Shortly after the squad's deployment, the group is attacked by an abnormal Titan, which results in the death of Thomas Wagner. This causes Eren to attack the abnormal in a rage, despite Milieus' warnings. Eren is injured, and the rest of the squad is killed trying to help him, with Milieus getting caught and eaten by a Titan.