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Eren has messy brown hair and teal-green eyes. Along with the other students, he wears the school's standard uniform that features black pants, a black jacket, a white long sleeve shirt, and white shoes.
Eren vows to kill every single Titan that stole his favorite lunch — cheeseburgers. He idolizes Levi and so decides to join the club he is in. Eren is an overall disorganized person who can be clumsy, reflected on the first day of school when he overslept and had to rush to school.
StoryEren wakes up from a long dream, drooling. Mikasa wakes him up but he panics enough to get himself dressed quickly, scared that he will be late for his first day. He is so distracted by his conversation with Mikasa he does not notice Christa and accidentally crashes into her. He apologizes by giving her little money to make up for making her drop her breakfast. Ymir splits them up and sends Eren and Mikasa off. Eren crashes into Sasha next, damaging her watermelon in the process. He gives her a small picture of him to apologize and she demands he pay for her watermelon. Afterwards, he collides with Mikasa at an intersection and is sent flying to the doorstep of Titan Junior High School. He finds the people from before trailing behind, all angry at him. However, they all hear the school bell and try to find their class. Eren accidentally runs into the Titan part of Titan Junior High, and tries to find his class 1-4. There, he is attacked by the dropping of giant stationery and notices that it belongs to a Titan. Everyone scrambles out of the classroom and are luckily found by Hannes. Eren is properly directed to his actual classroom, where he passionately introduces himself as the person who will eradicate Titans from the entire world. Eren's thoughts are intercepted by Jean, and they start fighting. Mikasa breaks up their fight and Jean blatantly shows his jealousy of Eren. Their fight is stopped by their teacher this time. Later on, Eren assembles with the rest of the first years to get welcomed by their Colossal Titan principal. Eren sees that their principal has kicked a hole in their school Wall and Titans are invading, stealing people's lunches. He angrily grabs cleaning supplies as weapons and charges at the Colossal Titan by jumping off a roof, but falls to the ground mid-jump. The Colossal Titan steals his cheeseburger lunch and Eren is distraught.
Eren tells his classmates that Armin is absent due to the cold weather despite it being spring. With that in mind, he decides to go check on him later. Mr. Keith notifies him and his friends to give in their club admission forms by the next day or else they will be sorted into a club of Mr. Keith's own choosing. Eren and Mikasa finish buying meat buns and sweet drinks for Armin, however their food is stolen by a Titan. To their surprise, Levi comes to their rescue by knocking the Titan down and Eren is inspired by Levi's actions. He asks which club Levi is in, however Levi keeps that a mystery. Eren and Mikasa enter Armin's abode and have trouble getting him out of his room until Mikasa mentions the food they brought. Soon enough, Eren notes that there is a rip in Armin's futon. When Levi snatches Armin's futon away, Eren and Mikasa head downstairs to look for him. Mikasa finds a wings of freedom button belonging to Levi, so Eren suggests they look for him at school.
They easily find the club Levi is in, namely the Attack Junior High Scout Regiment and try to look for Levi there. Eren meets a variety of upperclassmen and is keen on joining the club. He asks about Levi's button, and Hange shows Eren a technique to summon Levi by throwing a plastic bottle in the wrong assorted bin. Levi smacks Eren in the head with his paper fan and returns Armin's futon. Eren recovers quickly and is convinced to join the club. Eren and his friends are approved for admittance, but Eren is assigned to the Wall Cleanup Club due to the Attack Junior High Scout Regiment being unauthorized.Eren is excited for the next day's dodgeball tournament and is confronted by Annie, threatening him. The following day, he oversleeps causing his groupmates to do sacrificial ways in order to win. In the midst of Jean being almost caught disguising as him, Eren arrives. Mikasa runs to him, warning Eren that being late is not a good practice. The game continues as Annie attacks; Eren gets face smashed; and Mikasa trying to keep him safe. With the three of them left, Eren charges the ball to Annie as she forcefully kicks it back to him, sending Eren flying to the air. As he comes back to his senses, Eren asks Annie about her hatred of him. Annie reasons out her denial of her love to cheeseburgers as the cause of her grudge against him. Eren offers up a hand, apologizing to her as they make up.
Next day at lunch time, Eren drops his only cheeseburger for lunch. Annie requests to join him and his friends for lunch as she gives a cheeseburger to him. Eren is delighted and Annie offers another one, only for Mikasa to shove fish into his mouth. Eren assumes the act as Mikasa treating him like a child.
Due to the illegitimate approval of the Scout Regiment Club, Eren and the others find themselves cleaning the new building's windows from the orders of the Wall Cleanup Club captain, Rico Brzenska. Eren mocks himself for being a loser and envies the other students in much more fitting clubs. Irritation surges through Jean as he leaps off the window, with Eren and the crew reminding him that they are in the 3rd floor of the building. Afterwards Rico takes down an escaping Jean, she introduces the omni-directional mobility gear to the group, catching Eren's attention. Jean and him fight over the gear as Rico declares an agreement to teach them if they have done their task. Moments after, Rico checks on them only to be approached by a bright light coming from the windows thoroughly cleaned. Rico then proceeds onto her promise with Eren and the gang.Unluckily for him, Eren finds himself hanging upside-down from the gear. He goes through a repetitive process of banging his head and fails to use the gear properly. Mikasa tells him to give up, but Eren declines, recalling the thoughts of previous Titan attacks that brings him to the goal of their total destruction. Eren is enraging until Armin points out that it can be a possibility that a broken gear is handed to him, thus the cause of his infinite fall. As Mikasa glares at a mistakenly assuming Rico, Hannes comes over and teaches Eren the right way to use the gear. Tough-luck the gear busted and Hannes collides with Jean causing them to topple on top of each other. Hannes confronts Eren, saying he lacks the experience and reasons out his own failure due to drunkenness. Rico hurriedly points out the broken gear and dismisses the activities.
The next day, Eren is able to balance on the gear, thinking to himself that Mikasa should stop treating him like a child. On the other hand, Mikasa explains Eren's happiness is because he can now clean the Wall with her. Suddenly Sasha senses trembling which originates from a bunch of Titans heading for the Wall. Eren along with Rico and the gang take cover behind the trees. Enraged, Eren grabs off Mikasa's broom and attempts to attack one of them. Unfortunately, his gear runs out of gas and Eren smashes through the paintbrush dipped in red paint. Though he failed, Eren curses to eliminate the Titans once and for all.
- Mikasa Ackermann - Although Eren does not really pay attention to Mikasa's acts of affection towards him, he tries to get along with Mikasa despite her babying him. He acknowledges that she excels at everything she does and strives to beat her to prove his usefulness. As they were close since young, they have a casual friendship.
- Armin Arlelt - Armin is Eren's best friend and they were friends since childhood. Eren tries his best to make Armin realize his potential as a person, despite being a current shut-in. Eren is very supportive of Armin's ideas, often encouraging him to voice his opinion when he wants to.
- Levi - Eren bluntly idolizes Levi from his strength as "the strongest man" to his role in the anonymous band "No Name". Simply put, Eren aspires to possess Levi's demeanor when defeating Titans and is dedicated to the Attack Junior High Scout Regiment after hearing such an individual took part in the club.
- Jean Kirschtein - The pair often argue a lot due to differing opinions and personalities. Even though Jean brags to Eren most of the time about his popularity in elementary school, Eren does not feel inferior to him.
- Grisha and Carla Jaeger - They are the parents of Eren who wish him a good day at school. Although their relationship is not fully shown, it is implied that they are very close as a family.