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Dr. Jaeger has a gentlemanly appearance. He has straight brown hair and brown eyes with circular glasses. He wears a brown suit with a white cravat and a white shirt with ruffled sleeves. He has also been seen wearing a small, black hat with a gray stripe.
Years before the Fall of Wall Maria, Grisha Yeager was making a house call, with Eren tagging along, to Mr. Ackermann and Mrs. Ackermann for an appointed medical examination in the year 844. When he arrived there, he found them dead for hours. He asked Eren if he had seen the girl named Mikasa anywhere, but he was too shocked to answer. He then told Eren to wait for him at the foot of the mountain while he finds the Military Police. After the MPs and Grisha arrived at the murderers' hideout, Grisha hugged Eren and scolded him for the murders he committed when saving Mikasa, asking if he even understood what he had done. However, instead of continuing to scold him for killing Mikasa's kidnappers, he tells him that this time he was lucky and he could have been killed himself. Mikasa, cold and depressed, asked Grisha in what direction her home was and stated that she was cold and wants to leave. In response, Eren gave her his scarf and Grisha told her to come live with them.
StoryMikasa Ackermann. He keeps the basement of his house locked and does not allow anyone inside. Before departing to a journey, he promises Eren that he will show him what was in the basement when he gets back.
After the fall of Wall Maria, a tearful Grisha injects a serum into Eren's left arm, which Eren believes is responsible for giving him the ability to shift into a Titan. Telling Eren that the serum will cause him memory loss, Grisha gives him the key to the basement, saying that all of the answers can be found there, and that "their memories" will guide him.
After Eren finally succeeds in the use of vertical maneuvering equipment, head instructor of the 104th Cadet Corps Keith Sadies expresses to himself that Grisha would be proud of his son, Eren, and that he is finally becoming a soldier.
During his interrogation with Kitz Woerman, Eren Jaeger recalls an interaction with his father on the night of the Fall of Wall Maria. During this time, Grisha gives Eren the basement key and forces him take an injection that suppresses his memories. He tells Eren that he must let their memories guide him and get to the basement. He speaks of the harships he will face and is adamant that he must learn to control his power and save Mikasa's, Armin's, and everyone else's lives.
Grisha was a very skillful doctor, and served many families within the Walls. He was able to cure hundreds of people from a sickness that attacked mankind during his time in the Walls.
- Eren Jaeger - Grisha was perhaps closer to Eren than anyone else in his life, surpassing even his relationship with Carla. As a father, Grisha left home a lot on medical duties, however, he encouraged Eren's dreams to venture outside the Wall and offered to reveal to him the secrets of the basement.
- Carla Jaeger - When Grisha heard of Wall Maria's downfall, he shed tears in fear that his family had perished. Grisha was visibly affected by her death and when turning Eren to a Titan, was told that her death has made him crazy as his son screamed.
- Mikasa Ackermann - Grisha knew Mikasa when she was a small child from visiting her home as the family doctor. When taking Eren along for a visit he had hoped that the two would be able to get along as friends. After her rescue from the human traffickers, Grisha showed sympathy toward Mikasa and told her to come live with him and his family. Years later, after the fall of Wall Maria, Grisha mentions her name as he sheds tears in fear that she had been killed by the Titans.
- Mr. Ackermann & Mrs. Ackermann - Dr. Yeager was well known to the Ackermanns as their family physician. They appeared quite friendly when speaking about each other, and Grisha had been known to have been their Doctor at least since Mikasa was small, however it appears that as she grew older his visits were less frequent. Grisha seemed quite disturbed at the sight of their deaths.