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|Even if every other creature alive comes to hate you, your father will always be on your side.... So please. Promise me...that you'll come back!|
|— Mr. Leonhart to Annie|
Mr. Leonhart (レオンハートさん Reonhāto-san?) is an Eldian living in Marley and the father of Annie Leonhart. He had trained his daughter to be a Warrior candidate and she was selected to inherit the Female Titan's power.
Mr. Leonhart has a receding hairline with his dark hair combed back. He appears to be a relatively short man, and well built for fighting as he is a trainer. He has only been seen wearing a light jacket over a white shirt with dark pants and shoes. During the Liberio festival, he is seen wearing a beret and using a cane, which could mean that he is disabled.
He seems to be a relentlessly strict trainer, not allowing his daughter to take breaks and yelling at her during the training sessions. However, sometime before Annie's departure, he has a change of heart and apologizes to her, saying that she come back someday, and assuring her that he would always be on her side.
Mr. Leonhart taught Annie fighting techniques that involved kicks and the use of the opponent's weight against themselves. Before Annie left Liberio to partake in the Paradis Island Operation, Mr. Leonhart apologized to her, saying that it was too late to ask for forgiveness. However, Mr. Leonhart assured her that even if the whole world hated her and treated her like an enemy, he would always be by her side. He asked her only to promise him that she will return home.
After impressing Eren Yeager with her fighting technique during training, Annie mentions that her father was the one who taught it to her. She goes on to deride the ideals he held, comparing them to Eren's, and claiming that they have nothing to do with reality.
While Annie is trying to escape from Stohess District transformed in her Titan form, she remembers the last words her father said to her before she left Liberio. This memory triggers her hardening ability, encasing her into a crystal cocoon and allowing her to avoid interrogation, although she is captured and placed underground.
While waiting for the Survey Corps to arrive in Shiganshina District, Bertolt recalls the moment during the battle for Trost when Reiner Braun pressured Annie into taking Marco Bott's vertical equipment, claiming that it would prove that she, and her father who is waiting for her return to her hometown, are different than the "evil race" within the Walls.
Mr. Leonhart attends Willy Tybur's production at the Liberio festival, being seated in reserved seats meant for honorary Marleyans. He speaks with Karina Braun about Bertolt Hoover's father having passed away, and Mrs. Braun discusses the pride of both Annie and Bertolt having devoted their lives for Marley. Mr. Leonhart denies this, adamantly stating that Annie is not dead, as she promised to come home.
Mr. Leonhart listens apathetically whilst Willy delivers his speech, seemingly caring little for his revelations on the true history of the Great Titan War, or his reasons to wage war on Paradis Island. After Willy officially declares war, the Attack Titan comes forth, killing Willy and sending building wreckage into the crowd. Mr. Leonhart avoids the carnage and tries to assist Mrs. Braun in escaping.
- Annie Leonhart - At first he seemed to be a strict and not very approachable father for Annie, though for some reason he later changed his mind and demonstrated his love for his daughter by tearfully hugging her and assuring her that he would always be on her side. This reaction seemed to deeply surprise Annie, indicating that it was not common in him until then.
- Karina Braun - While they knew each other, they did not seem to be close. During the Liberio festival, Mr. Leonhart said they had not met since Karina's son, Reiner Braun, returned to Marley four years earlier.