Jiro Kusano, widely called Roji (a reversal of "Jiro"), acts as Toru Muhyo's assistant at their supernatural investigation bureau. His journey into magic law began after witnessing an executor save a possessed childhood friend, though he later failed the entrance exam for the practitioner academy. Roji accidentally met Muhyo during an interview advertised "No magic law experience needed" and secured the position after instinctively using a staff to injure a grudge spirit during a ghost attack at his hotel, revealing unexpected potential despite zero formal training. Roji embodies a kind-hearted and empathetic nature, frequently seeing the good in both people and ghosts—an idealism that sometimes leaves him vulnerable to exploitation by malicious spirits. He diligently studies and supports Muhyo to compensate for his initially weak magical abilities. Despite a tendency toward anxiety and moments of insecurity, he displays unwavering determination, especially in protecting Muhyo, cementing his role as the emotional core of their partnership. His significant latent spiritual power, once a dangerous vulnerability attracting ghosts due to uncontrolled energy leakage, was stabilized in childhood by Page Klaus, who gifted him "The Swallow that Defies the Wind" bolo tie to suppress this energy. In combat, Roji wields a magic pen to inscribe spells on seals for defense, support, or direct binding, mastering a technique to immobilize spirits by writing spells directly onto them. His unique "Super-Fab-Tech" hobby involves engineering intricate costumes and gadgets, showcasing proficiency in mathematics and physics. His abilities evolve substantially throughout the series: he temporarily wields tools usually reserved for higher-ranked practitioners and proves pivotal in major conflicts, such as disrupting the villain Teeki’s plans when adversaries underestimate his importance to Muhyo’s effectiveness. Roji's personal traits include near-sightedness (corrected by contacts), motion sickness, and a fondness for tea, sweets, and cute items. He maintains a close bond with his grandmother and expresses deep loyalty to Muhyo, whom he admires despite an intimidating demeanor. His character development involves confronting fears and embracing unconventional strengths, solidifying his indispensable role in their supernatural endeavors.