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The name used is an alias, nickname or surname found in an official source, but the actual in-universe name of this person is unknown in this continuity.
Doctor Yeager has a fairly youthful appearance and is well groomed, with his hair parted down the middle and clipped at his jawline. He wears circular glasses and keeps his facial hair styled in a mustache with a small goatee. For clothing, he is seen wearing a button down shirt with a bolo tie underneath a hooded cloak.
Doctor Yeager is a kind man. He enjoys his job as a doctor and helps his patients without a second thought. He also has a grim outlook on life, shown when he claims two men who hurt Eren got what they deserved when they died.
In the year 844, Doctor Yeager visits the Ackerman household in order to perform a checkup on Mrs. Ackerman. He brings his son, Eren along with him. Later in the day, Eren and the Ackermans' daughter, Mikasa tell the adults that they found three bodies while playing in the woods. As Doctor Yeager and Eren are leaving, Doctor Yeager tells the Ackermans that he will report the bodies to the Military Police at the base of the mountain. Doctor Yeager continues to visit every ten days in order to perform checkups.
A few weeks later, during one of his checkups, Doctor Yeager and Mrs. Ackerman start to laugh as they overhear Eren telling Mikasa that babies are delivered to mothers' stomachs by a huge bird.
Sometime later, Doctor Yeager is called early to the Ackerman household. Mr. Ackerman apologizes for calling in Doctor Yeager early and explains that Mrs. Ackerman has been bedridden for three days. Doctor Yeager tells them that fever is going down but due to the fact that Mrs. Ackerman is pregnant he will start performing checkups every five days. As Mikasa hands Grisa a wet towel to put on Mrs. Ackerman's head, he tells Mikasa that he will bring Eren with him too.
During a later visit, Mikasa notices that Eren has some bruises on his face and Doctor Yeager explains that he got in a fight with some other boys. After Doctor Yeager returns home he receives a letter from the Ackermans explaining that he left his hat at their home and they are sending Mikasa to return it. Doctor Yeager sends Eren to meet up with Mikasa once she gets to Shiganshina District.
Later in the day, Mikasa brings a severely injured Eren back home to the Yeager household. Doctor Yeager tells his wife, Carla that he asked the two about what happened but the two children responded saying that Eren tripped. Carla tells that she suspects Eren made her promise not to say anything.
The next day, Doctor Yeager escorts Mikasa back home. On the boat ride, Doctor Yeager tells Mikasa that he as asked an acquaintance of his in the Garrison to look into Eren's case. He asks her for hints to help find the people who hurt Eren but Mikasa hesitates before saying nothing. Doctor Yeager tells Mikasa that he is considering moving Eren to the mountains where Mikasa lives, in hopes that he can control his rage. Doctor Yeager says he believes that Eren may have a dangerous driving force inside him that made him get into the situation where he got hurt. Mikasa suggests that he has a great power inside of him and Doctor Yeager agrees, suggesting that maybe Mikasa could be the one to protect him from it. Doctor Yeager takes Mikasa to her home and bids the Ackermans farewell.
During his later visits to the Ackerman household, Doctor Yeager goes alone. Mikasa asks him if Eren is still recovering from his injuries to which he confirms. As Doctor Yeager leaves, Mikasa hands him a letter to give to Eren.
In the winter, Doctor Yeager reveals that Mrs. Ackerman has developed pregnancy toxemia which could harm her baby. He suggests that the Ackermans move to Shiganshina to a house near his. Five days later, Doctor Yeager helps the Ackermans move. While moving some boxes, Doctor Yeager is approached by his friend in the Garrison.
Doctor Yeager sits down with Mikasa at a table and shows her sketches of two men. He asks her if the two men in the sketches are the ones who hurt Eren. He also tells her that is she wants to keep her promise to Eren, she only has to nod. Mikasa nods in response. Doctor Yeager tells Mikasa that the two men are dead. He explains that Garrison used eyewitness testimony to identify the men. When the Garrison approached them, the men rain towards a crowded street and got involved in a carriage accident. Doctor Yeager tells Mikasa that witnesses claim Eren hit them out of nowhere but what they did to Eren was unforgivable and they got what they deserved.
- Eren Yeager - Eren is Doctor Yeager's son. Doctor Yeager fears that there is a dangerous force inside Eren that could lead him into harm's way.
- Carla Yeager - Carla is loving Doctor Yeager's wife.
- Ackerman family - Doctor Yeager is their trusted family doctor.
- Hannes - Hannes is Doctor Yeager's friend in the Garrison. They are close enough that Doctor Yeager is able to ask favors of him.