Known as Kazu to his friends, is a childhood friend of Ikki who becomes influenced to take up AT and join Kogarasumaru. He is originally bullied by Ikki as a child, and he often feels like others are more important than himself, especially compared to Ikki's natural talent. In the manga, Kazu owns a dog named Chiwa. He takes up running at a later point, which eventually leads to him being an exceptionally fast AT rider. As he shows signs of following the Flame Road, Spitfire takes an interest in him and eventually proclaims Kazu to be the next Flame King. He is given the Flame Regalia before Spitfire's death, Kazu soon discovers this during his challenge to be the hero who saves the fallen from hell. Kazu soon realizes that he truly wants to fight against Ikki and they began their battle. Kazu fights an amazing battle against Ikki. Though it seems that Ikki had gained the upper hand, he left the fight a draw. Kazu was very satisfied with how he had become close to Ikki's level. It has been revealed that Kazu has adopted not only Spitfire's techniques, such as Afterburner, but also Aeon Clock's Time Manipulation, which he has been taught by the advanced training program left in Spitfire's ATs. Kazu has recently copied a trick called "Flame Lens" from his opponent. This allows him to create an illusion of himself and Agito and win them their fight. This trick is considered to be above special A-class and is a very powerful technique for a (tentative) king to use without regalia.
Kazu is probably unaware of Emily's feelings for him and maybe does not reciprocate them, but he does show special attention to her from time to time, like rescuing her necklace when a rival threw it into a river, holding her hand after the team was defeated by the White Wolves or hugging her after she retrieves the balloon in the match against Inorganic Net (former Sleeping Forest).
He also normally represents a sort of morality when it comes to women, whereas Onigiri and Ikki are more lecherous. For example, when Onigiri caught up with Croissant Mask (Ringo in disguise) during their first parts war in order to look at her ass, Kazu was embarrassed while Ikki was envious. It is revealed that Kazu has an older sister and lives with her, as his parents are overseas and rarely around.