Klaus is the leader of the spy team Lamplight and a central figure in the anime Spy Classroom. He was the sole survivor of the legendary spy team Inferno, which was destroyed in a mission. In the aftermath of his former team's demise, Klaus set out to create a new team dedicated to tackling Impossible Missions, operations where the chance of failure is extremely high. He recruited a group of eight girls considered washouts from their respective spy academies to form this team. Klaus is around twenty years old, stands one hundred eighty-three centimeters tall, and uses the code name Bonfire.

Klaus possesses a remarkably calm and composed demeanor, even in the most dangerous combat situations. He is deeply eccentric and supremely confident in his abilities, frequently referring to himself as the World's Strongest Spy. A distinctive verbal habit is his frequent use of the phrase "It's marvelous" to describe situations that others might find dire or complex. Despite being a genius in espionage and combat, he struggles immensely as a teacher, finding it difficult to convey the intuition and logic that drives his own success to his students.

His primary motivation stems from the trauma of losing his former comrades in Inferno. He is driven by a fierce desire to protect the members of Lamplight and ensure they survive their perilous assignments. Initially, this manifests in a tendency to shoulder all the responsibility and danger himself, believing he must act alone. As the story progresses, his motivation matures into a genuine desire to nurture and trust his students, teaching them to rely on one another as a cohesive unit.

Klaus serves as the mentor, commander, and a father figure to the eight girls of Lamplight. He orchestrates their training and deploys them on missions, deeply influencing the narrative as a guiding force. The creator of the series has described Klaus as the protagonist of the story, comparing his role to that of a producer guiding the main performers.

His relationships with the individual members of Lamplight are distinct. He shares a mentor-student bond with Lily, the team's acting leader, who constantly strives to prove her growth to him. Grete, the master of disguise, harbors deep romantic feelings for him and is driven to excel in missions to earn his approval. The highly talented Monika views Klaus as the only person she considers a true peer, while the seduction specialist Thea shares a mutual understanding with him regarding the darker aspects of their shared profession. All the girls look to him as a source of stability and strength, and he gradually learns to see them as more than just students. A significant relationship from his past is with his former mentor, Guido, whose history with Klaus is a source of deep conflict.

Klaus undergoes a significant personal transformation. He begins the series as a solitary genius, emotionally scarred and convinced that he must work alone. His development involves learning to overcome this trauma by trusting his team and recognizing their individual strengths and abilities. He evolves from a lone operative into a genuine leader and teacher who values the collective strength of Lamplight.

His abilities are exceptional, cementing his reputation as the world's strongest spy. He possesses complete mastery of general espionage techniques, including combat, intelligence gathering, strategic planning, and infiltration. His logical mind remains sharp under extreme pressure, allowing him to navigate and deconstruct the most complex threats. Outside of his spy work, he enjoys painting with oils and watercolors, which highlights a contemplative side to his character.