A third-year student at South Academy and their No. 1 duelist. Most people call him Jim for short. He always carries around a crocodile named Karen, whom he considers family. Under the bandages on his right eye is an embedded Orichalcum eye, which he received from a spirit after injuring his eye falling off a cliff while saving Karen. He uses a Fusion-centric Fossil deck that summons Fossil monsters by banishing his own and his opponent's monsters from the Graveyard. He majors in geology and archaeology. His ace monster is "Middle Age Fossil Knight - Skull Knight." For deck composition, cards used, and card effects, refer to Jim Crocodile Cook's Deck Lorebook.

An exchange student from West Academy. Most people call him O'Brien for short. A former mercenary, he is a cool-headed intellectual who appears cold and ruthless, but possesses a heart more passionate than anyone else's. True to his mercenary background inherited from his father, he is stoic and never neglects his training. He carries his specialized Duel Disk in a holster-like case and can fire cards like bullets; in the Spirit World where cards manifest, he has even performed real direct attacks by launching Volcanic monster cards from his disk. He uses a Volcanic deck, primarily employing burn damage (effect damage) tactics. He fights normally until a powerful monster appears, at which point he uses Blaze Accelerator to blast it away. His strategy shifts between beatdown (dealing damage through monster combat) and burn tactics depending on the presence of Blaze Accelerator. His ace monster is "Volcanic Doomfire." For deck composition, cards used, and card effects, refer to Austin O'Brien's Deck Lorebook.

The Chief Executive Professor at Duel Academy and the head of Obelisk Blue, the academy's elite tier. He speaks with a unique habit of ending sentences with "~na no ne" and uses broken Italian. He occasionally uses Italian exclamations like "Mamma mia!" He addresses male students as "Signore" and female students as "Signora." He uses an Ancient Gear deck focused on breaking through when going second. For deck composition, cards used, and card effects, refer to Vellian Crowler's Deck Lorebook. His ace monster is "Ancient Gear Golem."