Gaius Levina Sorel is one of the two protagonists of the story, a young man who works as a professional offensive jushikiist in the city of Eridana. He has a lean build, blue eyes, and red hair that grows to his neck. Unlike his partner, Gaius is a deductive and intellectual individual who approaches problems with analysis and caution. He tends to be more reserved and hesitant compared to his partner, preferring to follow procedures and think situations through carefully. Despite his competence as a jushikiist, he is constantly worried about his financial state, a concern compounded by his partner's habit of spending money on frivolous items such as excessively elaborate furniture.

As a jushikiist, Gaius takes on a variety of dangerous requests from clients, ranging from eliminating bandits and dealing with dragons who have violated treaty lines to stopping vengeance-driven killers and confronting terrorists. His role in the story is fundamentally tied to his strained but effective partnership with Gigina, a warrior from the Drake culture. Where Gigina is hotheaded, melee-oriented, and obsessed with battle and glory, Gaius serves as the analytical counterpart, the brains to Gigina's brawn. Their dynamic is defined by constant bickering, insults, and mutual frustration, yet they possess a deep-seated trust and always support each other when truly threatened. This partnership is complicated by the fact that Gaius lost a loved one to dragons, making his alliance with Gigina, who comes from a dragon-worshipping background, an uneasy one.

Gaius maintains a significant romantic relationship with his girlfriend, Jivunya, an Arlian woman who constantly worries about his safety. Their relationship is depicted as stable and physically intimate, though it is frequently interrupted by Gaius's work obligations. He also has a contentious working relationship with his superior, who is constantly belittling him, cutting his pay, and blaming him for disasters beyond his control. A tragic element of his past is the loss of his sister, Aleciel, when he was younger, an event that served as a primary motivation for him to pursue training as a jushikiist. Backstory episodes delve into his earlier days as an overeager and untrusting youth, shedding light on how his initial partnership with Gigina began and the origins of his relationship with another associate named Cuello.

In terms of abilities, Gaius is a high-level offensive jushiki user, capable of channeling magical formulas through bladed weapons to fire projectile attacks, making him more focused on ranged combat than his melee-oriented partner. One of his most notable tools is his glasses, which possess analytical capabilities that allow him to assess opponents and quickly deduce information, such as identifying a body double through subtle body language. His intellectual nature and skill at analysis are defining features of his combat style and his role within the central partnership.