Rohm Zahn is the eldest son and heir of the Zahn Clan, a powerful criminal syndicate dominating the SAU underworld. He is the older brother of Aiko Zahn. Ordered by his father, Rubian Zahn, to compete in the Urdr Hunt—a competition offering substantial rewards—Rohm understood that leadership of the family would go to whichever son achieved the best results. He operates under the assumption that succession is his guaranteed right solely due to his status as firstborn.

Rohm exhibits a brutal nature, treating individuals known as "human debris" with contempt and viewing them as disposable garbage. This harsh demeanor contrasts with his personal preference for the color pink. During the Urdr Hunt, Rohm and his brother traveled to the Venus Sphere, possessing one of the participant rings, accompanied by their guide Bellows Xhosa. Rohm actively schemed against rival participants. When conflict erupted between Renzie Dablisco of the Omden Colony Company and Wistario Afam, Rohm devised a plan to intervene and eliminate both competitors simultaneously to increase his own chances of success.

The conclusion of the original Urdr Hunt mobile game service left the overall hunt storyline, including Rohm Zahn's fate and ambitions, unresolved. The Urdr Hunt Special Edition film compiles and re-edits the game's story with new scenes but provides no further development or resolution for Rohm's character arc beyond his established role as an antagonist within the competition.