Klaus was a man of average height and build, with short brown hair. When not wearing the standard Scout Regiment uniform, his attire consisted of a button-up shirt and dark pants.
Klaus seemed to be a very straightforward man. While discussing Grisha Jaeger's past, Klaus expressed doubts at Grisha's loyalties, sarcastically noting that Grisha should have helped the Scouts more if he truly supported them. He displayed this trait again when the Scouts begin fighting each other over meat, noting that it was a bad idea to have riled them up with good food.
Klaus is seen attending a meeting with Erwin Smith and the rest of the Scout Regiment's officers to discuss the recent revelations about Eren Jaeger's father Grisha. As the officers depart the meeting in high spirits, Erwin informs them he will leave the teams up to them with Klaus reflecting they should keep the task a secret.
Later on he is seen eating with his fellow leaders as fighting breaks among the Scouts over the meat that is being served in celebration for their next mission.
As the Scouts prepare to depart for Wall Maria, they are met with unexpected fanfare from the citizens of Trost. Klaus is stunned by the commotion, noting that the Scouts have never received such fanfare. They are all silenced by Erwin, who begins cheering as well and orders the Scout Regiment to begin its mission to reclaim Wall Maria.
After the Scouts successfully seal the hole in Wall Maria they are attacked by the Beast Titan and its forces. Erwin orders Klaus's team to protect the Scouts' horses with Dirk and Marlene's teams and Klaus relays the orders to his recruits. During the fighting, Klaus and his fellow soldiers are killed by the Beast Titan, who starts throwing crushed boulders at them, cutting them all to pieces.
When Hange decides to oppose Eren's plan to destroy the world beyond the Walls, Klaus is one of the soldiers remembered while Hange tries to convince Jean and Mikasa that their fallen comrades would not support destroying the world.
- Klaus and Koslow share the same Japanese voice actor.