Kazuma Mikura, known to his friends as Kazu, is a central character in the Air Gear series and serves as a foundational member of the Kogarasumaru team. He is a fifteen-year-old student and the childhood friend of the protagonist, Itsuki Minami, who is called Ikki. Kazu lives with his older sister while his parents work overseas and are rarely home.

Kazu is defined by his quiet and earnest personality, but his most prominent trait is a profound lack of self-confidence. He constantly feels overshadowed by the natural, effortless talent of his friend Ikki, which leads him to underestimate his own significant abilities. This insecurity makes him prone to fading into the background, earning him the nickname transparent man, and he often becomes nervous when placed in a leading role or in the spotlight. To compensate for his perceived lack of innate talent, Kazu becomes the most dedicated member of his team, training harder and more frequently than anyone else. His loyalty to Ikki is absolute, and he will fiercely defend his friend's honor, even when it means fighting against overwhelming odds. Despite being surrounded by his friends' more lecherous tendencies, Kazu often represents a more level-headed and moral perspective, particularly when it comes to matters involving women.

His motivation is intrinsically tied to his relationship with Ikki. Initially, Kazu is driven by a desire to not be a burden and to stand alongside his more talented friend. However, this dependence also becomes a source of his insecurity. For a period, he is forced to act as the interim leader of Kogarasumaru while Ikki is hospitalized. During this time, his self-doubt resurfaces and the team suffers a loss he feels responsible for, which deeply hurts his morale. A major turning point in his character development occurs when he inherits the Flame Regalia from the previous Flame King, Spitfire. The weight of this responsibility and the trauma of witnessing Spitfire's sacrifice to protect him cause Kazu to spiral into a deep depression, especially after the Regalia is stolen. His eventual recovery and renewed resolve come from confronting and battling a disguised Ikki, an act that forces him to step out of his friend's shadow and fight for his own identity as the new Flame King.

Within the story, Kazu transitions from being Ikki's dependable sidekick to a king-level rider in his own right. His role on the team is that of a loyal second-in-command and the group's most diligent trainer. As a storm rider, he is classified as a speed-type, often characterized by the series' author as a jet plane due to his incredible velocity. His key relationships are with his mentor, Spitfire, who recognizes his latent potential and bequeaths him the Flame Regalia, and with his rival and friend, Aeon Clock, who both challenges and aids him. These relationships are central to his growth from a boy who hides in the shadow of a natural genius to a determined king who fights for his own place at the top.

Kazu's notable abilities are centered on the Flame Road, which he manifests not through actual fire, but through super-speed that creates the illusion and sensation of flames. His signature techniques rely on overwhelming velocity. After Burner allows him to accelerate to supersonic speeds, leaving trails of fire in his wake. Perhaps his most famous trick is Time, in which he strikes specific nerve points on an opponent's body at high speed, temporarily paralyzing them and giving the illusion that time itself has stopped. As he grows into his power as the Flame King, he also demonstrates advanced abilities such as the Shield of Time, which slows incoming attacks, and the ultimate technique Heaven's Door, which allows the user to perfectly replicate the tricks and roads of other riders by accessing a data archive through the Regalia.