Jiro Kusano, known almost universally by his nickname Roji, is a main character who serves as the assistant to the genius executor Toru Muhyo. His nickname is a simple reversal of his given name, Jiro. Roji's journey into the world of magical law began in childhood after a friend became possessed by a ghost. An executor was called in to resolve the situation, and witnessing this exorcism inspired Roji to pursue a similar path. However, his initial attempt to join the field was unsuccessful, as he failed the entrance exam for the practitioner academy. His path then took an accidental turn when he saw a sign advertising an interview for an assistant position with the promise of no experience needed. He stumbled into the interview and met Muhyo, though the encounter did not go well, and Roji left believing he had ruined his chance. That night, a grudge spirit attacked the hotel where he was staying. In a moment of desperation while trapped by the creature, Roji grabbed a staff and instinctively channeled his spiritual energy, or Ren, into it, managing to injure the ghost. Muhyo arrived on the scene and, after dealing with the spirit, asked Roji why he had acted. Roji replied that he simply wanted to save everyone. A few days later, under special circumstances, Roji was hired as Muhyo’s assistant.

Roji is defined by his profound empathy and unwavering optimism, consistently trying to see the good in people and even in some spirits. This kind-hearted nature is his greatest strength, but it can also be a vulnerability, as his idealism sometimes makes him susceptible to manipulation by malevolent ghosts. He is a sensitive and emotionally expressive person, prone to anxiety and tearful outbursts, which often contrasts sharply with Muhyo’s stern and composed demeanor. Roji frequently complains about his situation or Muhyo’s intimidation tactics, which can annoy his partner. Despite this and his own frequent self-doubt, Roji possesses a deep well of determination and courage. He constantly studies to compensate for his initially weak magical abilities and takes significant risks to protect Muhyo and others, revealing a different kind of power in his kind and unwavering heart.

Roji’s primary motivation is to be a capable and reliable assistant to Muhyo, seeking his acceptance and approval. He is intensely loyal and dedicated to their work at the supernatural investigation bureau, handling duties that range from meeting clients and making tea to providing crucial support during exorcisms. At the start of his career, he holds the rank of Second Clerk. His role in the story is to act as Muhyo’s moral anchor and emotional core, often being the one who connects with the human element of their cases while Muhyo focuses on the legal and combative aspects. The dynamic between Roji and Muhyo is central to the narrative. Their relationship evolves from one of perceived disdain and Roji’s insecurity to a deep, mutual reliance. Muhyo, who secretly values Roji’s honesty and selflessness, chose Roji despite his lack of formal qualifications, and their partnership grows into a strong friendship built on trust and complementary personalities.

Over the course of the series, Roji undergoes significant development, growing from a second clerk with minimal combat skills into a more confident and capable magic law practitioner. He relies on a magic pen to create binding seals for defense and support, with his early signature ability being a technique called Direct Binding that allows him to immobilize ghosts by writing spells directly onto them. His power is deeply tied to his confidence and hidden potential, which emerges in times of crisis. It is eventually revealed that Roji possesses extraordinarily high tempering, or spiritual energy, which was so volatile that it attracted evil spirits. To suppress this dangerous energy, an executor named Page Klaus gave Roji a bolo tie, a gift that inadvertently stabilized his power and prevented further supernatural incidents. As the story progresses, Roji proves himself to be indispensable, even against powerful adversaries who underestimate his importance to Muhyo’s effectiveness, cementing his role not just as an assistant, but as a true partner. He is skilled in creating costumes and gadgets, a hobby he calls Super Fab Tech, showcasing a proficiency in engineering and design. He enjoys tea and sweets, dislikes ghosts and when Muhyo is frightening, and suffers from severe motion sickness.