Sannes is a tall man with a short crop of dark-colored hair and brown eyes. He is usually wearing the Military Police uniform but after his imprisonment, he wears typical jail attire.
Sannes is an individual who holds a strong sense of loyalty to the king and keeping the security of the Walls, to the point of adhering to the murder and torture of others regardless of who they are to maintain peace. Like most Military Policemen, he looks down upon those from the Scout Regiment, regarding them as useless goons who never get things done, unlike valuable soldiers such as himself. However, he has shown a degree of carelessness and did not take much caution when disposing of people viewed as threats, as seen when he revealed how he was aware of Nick's status in the Order of the Walls and how his valuables would be a motive for murder-robbery when the Pastor's identity was concealed as a chair craftsman without a single piece of luggage, Sannes also left signs of torture on Nick's body and evidence of torn skin on his own knuckles.
In spite of that, even when held captive and tortured, he refused to tell his abductors his knowledge about the Reiss family. He believes that humanity was able to come this far in peace and without war was due to the efforts and sacrifices of the First Interior Squad, who would quickly murder these threats, and how people should be grateful towards their actions. It is later revealed, however, that Sannes has feelings of guilt and regret for his own actions of the past as Levi and Hange continue to torture him, crying to them that they should have fun and continue to hurt him without holding back, finally coming to realize just how much pain he inflicted on others during his life, asking to be tortured to death as compensation.
Djel Sannes joined the Military Police out of an extreme sense of loyalty and desire to serve the king. As part of the First Interior Squad, one of Sannes' main jobs was to discretely dispose of any citizens who threatened the government's reign inside the Walls.
When a young boy began talking to his friends about his father's theories that the royal government had forcibly removed humanity's memories of the outside world in order to more easily control them, Sannes apprehended the boy's father and killed him.
Sannes later met the serial killer Kenny Ackermann while attending a speech that King Uri Reiss was giving to the Order of the Walls. Kenny attempted to apologize for killing a large amount of Sannes' comrades during his time as a killer, but Sannes was unconcerned as long as the man was now loyal to the king.
Sannes is among the Military Police members who accompany Kenny Ackermann to kill Rod Reiss' mistress and his illegitimate daughter. Although they kill Alma, Rod convinces them to spare Historia by giving her an alias to live under.
After receiving word that Pastor Nick from the Order of the Walls has divulged valuable secrets to the Scout Regiment, Sannes and Ralph are ordered to find out how much he told. Visiting the man, the two savagely beat and torture Nick. Despite their best efforts however, Nick refuses to talk and eventually dies without saying anything.
Sannes and Ralph cover up the torture by claiming that Nick was killed during a burglary gone wrong. When Nick's friend Hange Zoë attempts to investigate, Sannes refuses to allow her entry, claiming she will interfere with the crime scene. As Hange persists, Sannes forcefully grabs her jacket to inspect which unit she came from, but is held back by Moblit, who properly introduces Hange and himself.
Realizing that both soldiers are from the Scout Regiment, Sannes turns hostile and insults them. Hange expresses her shock to find a soldier from the First Interior Squad, but Sannes retorts that they are at least busy getting things done, before claiming that what befell Nick is not rare, considering his status. Hange apologizes, and entrusts the investigation to the two men and asks them to relay a message to the culprits before leaving.
Sannes later attends an audience with various nobles and King Fritz. The nobles express dissatisfaction with him for failing to get any information from Nick, but when he volunteers to continue searching for more information, Lord Reiss tells him that it will not be necessary.
Sannes and Ralph receive word that the merchant Dimo Reeves knows the location of Levi Ackermann and his squad. However, upon arriving, they find that Reeves has double crossed them, and they are swiftly taken captive by Levi's squad.
Not bothering to ask him any questions, Levi immediately begins torturing Sannes until Hange and Moblit arrive to help. Sannes, terrified, points out that they have yet to ask him any questions, but upon hearing what they want to know, refuses to talk.
After another round of torture, Hange shows Sannes all his pulled off nails and apologizes for not being as skilled as him, wondering aloud how many people had to torture to get so good at it. Sannes admits that the number is higher than he would like, but insists that what he did was necessary to maintain peace within the Walls, demanding that they be grateful for what the MPs have done for humanity. With tears in his eyes, Sannes comments on his jailers' cruelty, calling them monsters, but claims that they do not scare him, professing his devotion to the king. However, reflecting on how each of his victims experienced the same pain he is currently feeling, Sannes asks that they kill him.
The three torturers take a break, and Sannes is left alone. He soon hears Ralph's voice outside of his cell, and is shocked to learn that Ralph has apparently cracked from his torture, and revealed everything to their captives. Shortly after, his torturers return, and a broken Sannes readily reveals to them that the Reiss family is the true royal family.
He is later put in the same cell as Ralph where he tries to strangle him for betraying the King without hesitation but is stopped by Hange who tells him that Ralph has not revealed any information but was instead used as a means to have Sannes reveal everything. This causes Ralph to call Hange and the others devils, with Hange replying that Nick surely thought the same of his murderers and yells at Sannes to blame himself for his current state. Crying, Sannes wishes Hange good luck, but also states that one day, there will be someone to take on their role again.
- He and Mr. Rall share the same Japanese voice actor.