Karl Björn Andrésen commands the Marine squad aboard the United Planets Space Force destroyer *Soyokaze* as a lieutenant. His Marines operate as a distinct, insular unit with autonomy in their ship section, consistently displaying a rough and combative demeanor. They seek confrontations and resist senior officers—such as First Lieutenant Makoto Yamamoto and Lieutenant Commander Yuriko Star—who attempt to enforce order or cleanliness standards in their area.

Andrésen's squad employs specialized powered exoskeletons for combat, requiring a crouched piloting position due to their compact design. Standard troops wear yellow exoskeletons, while Master Sergeant Cryborne's is pink. Andrésen’s leadership mirrors his unit’s resistance to strict military discipline, yet he shows responsibility regarding equipment safety. During testing of a new Marine weapon system, he expressed significant concern based on prior knowledge of its designer. This apprehension proved justified when the weapon malfunctioned during deployment, creating a hazardous situation that demanded resolution.

His relationship with the *Soyokaze*'s star pilot, Lieutenant (junior grade) Kojiro Sakai, is notably antagonistic. Minor provocations frequently ignite conflicts between Andrésen’s Marines and Sakai, feeding the ship’s atmosphere of barely contained chaos.