Dirk was a man of average height and build, with long, dark blond hair that he kept pushed back out of his eyes. He also had a thin beard on his chin and cheekbones, and a small mustache. When not wearing the standard Scout Regiment uniform his attire consisted of a white button-up shirt, dark pants, and a black vest.
Dirk appeared to be a rather calm, serious man. When violence erupts among the other scouts, Dirk only made a casual note of their behavior, and made no effort to break up the fighting or intervene in any way. He demonstrated the more serious aspect of his personality when the citizens of Trost see the Scout Regiment off with fanfare, obviously dissatisfied with the commotion that they are causing despite admitting that the scouts have never received such praise.
He seemed to be a trusted subordinate, as he personally escorted and advised Erwin Smith during the Scout Regiment's mission to Shiganshina.
Dirk attends a meeting between Erwin and the other Scout Regiment officers to discuss the recent revelations involving Eren Jaeger's father. After the meeting, Dirk suggests possibly punishing Keith Sadies for withholding information from the Military, but Hange Zoë dismisses the notion, claiming that Keith is not worth the effort.
The officers decide to serve meat for dinner in celebration of the mission to retake Wall Maria. Fights break out over the meat being served, but Dirk and the officers choose to ignore them rather than intervene.
The day of the operation, all soldiers are ready at dawn. Dirk and other high-ranking soldiers salute to members of the other branches and head to the Wall. As the Scouts are preparing to depart, they are met with unexpected fanfare from the citizens of Trost. Dirk is annoyed that the news of their departure has leaked, but concedes that there has never been such fanfare for the Scouts before. He and the other scouts are silenced by Erwin, who begins cheering along with the crowd before ordering the scouts to begin their final operation to reclaim Wall Maria.
While en route to Shiganshina, the Scout Regiment switches to traveling on foot through a forest on a mountain, leading their horses. As they are traveling, Levi notes that it has taken them longer than expected to traverse the mountain and Dirk tells him that once they are past it they will have reached the district.
Once the scouts reach Shiganshina District, Dirk positions himself with Erwin atop Wall Maria while Eren seals the hole in the wall. Dirk is surprised to see that no one has tried to attack, and wonders if the scouts' forces are too much for Reiner and Bertholdt to handle. He is interrupted by the arrival of Armin Arlelt, and is shocked to learn that Armin has found evidence of a third person accompanying Reiner and Bertholdt. Erwin gives Armin command of the Scout Regiment so that he can look for Reiner and Bertholdt, prompting Dirk to comment on the big gamble Erwin has taken. He asks if the scouts will be staying until Reiner and Bertholdt are found, which Erwin confirms.
When the Beast Titan reveals itself and its forces, Erwin orders Dirk and Marlene's teams to meet up with Klaus's team at the district's gates and protect the scouts' horses. Dirk and his fellow soldiers fight off approaching Titans while the recruits in his team take the Scouts' horses to a safe place. After finishing the Titans on his side of the battlefield, Dirk reports to Levi that only a few Titans are left, and urges Levi to rest while he and the rest of the soldiers handle them. However, before he can engage any more Titans, Dirk and his teammates are cut down by a barrage of rocks thrown by the Beast Titan. Dirk, managing to survive the first wave of rocks, only has time to observe the corpse of one of his allies before being torn to pieces by a second barrage of rocks.