|I'm finally going to show you the results of my hellish training!|
|— Eren faces the Colossal Titan|
Eren has swirly celadon pupils with shaggy brown. He wears the standard Cadet Corps uniform.
Eren is overly obsessed with Titans, to the point where he blames them for every thing that happens to him, even when there are no Titans around, and is often seen overreacting to little things. He has a problem of being constantly late to his classes.
Eren finds that he has woken up late and has trouble going to class on his first day to the Cadet Corps school.
Eren worries over Armin when the latter suddenly faints during the morning assembly, and is later shocked to find out that Armin had simply dozed off. As he starts heading back, Mikasa hits Eren, knocking him out. Eren questions Mikasa after waking up, with her admitting that she does not want him to go back standing at the assembly.
Eren is having a bad training day and is later approached by Jean who offers to be teach him a trick to ODM training, but only feels that Jean tried to make fun of him when Armin points out that the trick does not relate to the training.
Armin brings an indecent book and shows it to Eren, with the latter having a nosebleed while look at its illustrations. When the commandant later confiscates the book, Armin convinces Eren and the others to retrieve it and the group ambushes the commandant in his office.
Running late to class, Eren accidentally walks in on the girls unbeknownst to him that they have been using the classroom as a changing room.
Eren is bedridden and misses the day of the cadets' mealtime pudding as a result.
On the cadets' day off, Eren attempts to head into town with Mikasa and Armin.
Eren dreams of fighting a Titan and wakes up screaming at night when it grabs him. He laments his lack of strength to beat the Titans, and Armin advises him to talk to Reiner. The next morning, believing that Reiner's daily routine is the secret to his muscles, Eren tries to imitate Reiner and competes with him during breakfast.
During hand-to-hand combat, Eren trains with Annie. When Mikasa intervenes due to Eren's injuries, the two girls decide to have him choose which one is more skilled, and later Eren ends up unconscious as a result.
Eren is shocked when Conny explains to him the logicality behind his crew-cut hairstyle and decides to shave his head as well.
During the test results day, Eren is distressed to find out that he had flunked. Armin offers to help him study, and later reveals that Eren's answers are nearly correct but were only off by one row.
Eren dreams of having to retake the same balancing drill where he failed to balance himself due to a broken clasp, but does not manage to succeed again in the dream and is sent off to the fields.
Marco finds a lost bag and consults his friends about returning it to the girls' room. Eren is unwilling to go with them at first, but changes his mind when Jean spites him.
Mikasa acts weirdly all day, and when Eren confronts her about it, he notices her hiding something behind her back and tries to get her to reveal it, but she ends up punching him in the face.
Eren attends the 104 Cadet Corps' graduation ceremony. When the Colossal Titan suddenly appears, Eren remembers all the times the Titan had appeared in and terrorized him, and vows to pay it back by showing it the results of his training. Eren, Mikasa, and Armin charge the Titan along with a group of other graduates, but they all end up eaten.
- Mikasa Ackermann - Eren is dependent on Mikasa, always relying on her to wake him up in the mornings. Despite this, he dislikes it when Mikasa becomes overly protective of him, lashing out at her on one occasion.
- Armin Arlelt - As his friend, Eren cares for Armin and the two are often seen together. When Eren struggles in tests, Armin offers to help him study. After a Titan eats Armin, Eren is horrified and seeks learning about Titan weaknesses in order to rescue him.
- Jean Kirschtein - Eren and Jean bicker most of the time, but the latter sometimes seeks the former's approval, due to Mikasa being part of his group, with Jean admitting to his jealousy of Eren. When Jean goes missing during an endurance test, Eren joins the search party.
- Annie Leonhart - During hand-to-hand combat training, Eren often trains with Annie and shows persistence in learning her techniques, despite ending up knocked over each time.
- Reiner Braun - Eren is impressed by Reiner's strong physique and aspires to be like him, observing and imitating his daily routine in order to learn the secret to his muscles, which Reiner finds his behavior to be confusing.
- Conny Springer - While initially not thinking of him as much, Eren is left astonished when Conny explains to him the logicality behind his hairstyle, which makes Eren consider Conny's dedication as a soldier to be higher than his.