Mark serves as Benno's leherl and primary assistant at his store, functioning as his trusted right-hand man. He sports short brown hair and maintains a professional merchant appearance, typically wearing a waistcoat layered over a white shirt. Dignified and thoughtful in professional settings, Mark demonstrates notable skill at work. Though generally kindhearted, he conceals a vindictive streak that surfaces when others disrespect Benno. His loyalty to Benno began in childhood during his Gilberta Company apprenticeship, solidifying when he supported Benno through the transition after Benno's father's death. This loyalty was tested when Mark's own family attempted to exploit the company's vulnerability after Benno's parents died. Disgusted by their betrayal, Mark actively opposed them, resulting in their store's ruin.

Within the narrative, Mark teaches practical skills like order form completion to Myne and Lutz while Lutz practices writing. He accompanies Myne during lumberyard visits and ensures her safe return to the Gilberta Company when she collapses. Intrigued by Lutz's early ability to write his name, Mark also finds Myne's calculator-free mental calculations fascinating, requesting lessons for calculator-free situations. Privately, he resolves to mentor Lutz, building the boy's resilience against demands from both Myne and Benno. Mark aspires to become Benno's "God of Fire"—symbolizing his commitment to supporting Benno's growth from behind the scenes.