Nile is a man of average height and build. He has short, thin, black hair that is cut shorter on the sides and back, and his eyes are dark in color. He also sports a very light mustache and goatee. He is always seen wearing the standard military uniform bearing the Military Police symbol, but also wears a red bolo tie similar to that of his fellow military commanders.
Nile prides himself on being a very rational individual. Whenever he is faced with a tough choice, he weighs all possible options and chooses the one that makes the most sense to him. He wanted to have Eren Jaeger executed, but was not blind to his usefulness like Pastor Nick was. He determined that the potential civil war within the Walls was too great a cost, especially considering the Scout Regiment could not guarantee anything about Eren. However, he relented his position when Levi brought up the fact that the Military Police would be ill-equipped to deal with Eren in his Titan form. Nile is never totally committed to one way, and will change his opinion as the situation develops. A similar instance is when he questioned Erwin Smith due to him violating laws and command structure, but allowed his plan to go on since the Female Titan was already released and it would be very difficult to stop it without Erwin leading the Scout Regiment.
Nile is seen at the place of the incoming trial of Eren Jaeger. He remarks on how the commoners are a rash lot for thinking of Eren as a savior and says that he will not let the Scout Regiment have Eren, and states that he will be disposed of by the Military Police. Nile and the rest of the soldiers then salute the head of all three Military branches, Premier Dhalis Zachary, who arrives at the location of the trial.
Nile appears as the leader of the Military Police during the trial, he advocates killing Eren due to the impending civil war, but he does analyze and weigh the different pros and cons of Eren before making his final decision. He recognizes that Eren's Titan powers had saved Trost District, but threaten the balance of power within human society. While mainly business and Wall Rose residents support Eren, most people of importance such as the clergy, view Eren as a danger.
Thus, Nile concludes that to avoid civil war, Eren must not be allowed to live. Eren responds by calling him and his group a bunch of cowards, and Nile wants to have him killed; however, Levi interferes by beating Eren in front of everyone. Dhalis Zachary ultimately places Eren in the Scout Regiment, and Nile is displeased that he lost the trial; however, he asks Erwin Smith how the Scout Regiment intends to perform a mission to Wall Maria.
After a battle breaks out in Stohess District, Nile questions Erwin's actions, saying that they are a clear act of treason against the Royal Government and, at gunpoint, orders him to remove his gear. Erwin admits that he acted on his own authority and this angers Nile, he grabs him by the collar telling him that he had to have known what this plan of his would have caused in the city.
Nile calls him a traitor and believes that none of the higher-ups will complain if he executes him now. Erwin then says that Nile will be in charge, telling him to not let the Female Titan escape. Nile interrupts him and asks if he really thinks this is for humanity's sake. When Erwin says he believes it will serve as a step forward, Nile orders his soldiers to lower their guns and cuff him. Going by his suspicions, he orders to deploy all troops and focus on evacuating the citizens, choosing to let a court of law decide how to execute Erwin.
When the royal government declares a freeze on Scout Regiment activity, Nile personally oversees the confiscation all of the Scouts' possessions. After Nile's soldiers have taken everything, Erwin asks to speak with him personally. Nile makes it clear that he is not interested, and becomes alarmed when Erwin begins musing about whether or not the government can be trusted, and demands to know what Erwin is planning to do.
When Erwin is arrested for the murder supposedly caused by the Scout Regiment, Nile visits him in his cell, letting him know that his audience with the King has been scheduled. Ignoring the news, Erwin chooses instead to ask Nile how his family is doing and where they are currently living. Taken off guard, Nile says they should be fine, though he has not been home in a while. They live in the eastern section of Wall Rose. Satisfied, Erwin tells Nile that he is leaving something up to Commander Pyxis, and if the time comes, he will be watching for Nile's decision.
The next day, Nile joins other military officials in the King's throne room for Erwin's audience. The meeting ends in Erwin being sentenced to death, causing Nile to wonder if everything is truly going as Erwin planned.
Before Erwin can be led away, Anka Rheinberger bursts in, announcing the fall of Wall Rose and that refugees are fleeing towards Wall Sina. In his shock, Nile remembers his conversation with Erwin and realizes that Erwin knew this would happen. As Pyxis tries to mobilize his forces to aid in the evacuation, the government officials order that the gates to Wall Sina be shut to all refugees. Though Nile tries to reason with the officials, as there is no guarantee that admitting refugees would cause a civil war, he is angrily rebuffed merely on the possibly that a war could happen. When he does not take action immediately, he is warned that disobeying would be treason. Nonetheless, Nile declares that he will not allow the gates to be closed.
At that moment, Premier Dhalis Zachary appears with a group of soldiers, revealing that Anka's announcement was a fabrication and Wall Rose has not been breached. The military arrests the officials in a coup d'état, finding them too selfish to rule humanity, and as they are led away, Nile concedes to Erwin that he has won his gamble. However, he is perplexed when Erwin is not happy with the result. Erwin warns Nile that humanity has been forced onto an even more dangerous path.