Jun Kenzaki, a boxing prodigy, enters the narrative when Ryuji Takane and his sister Kiku arrive in Tokyo. His immediate confidence in the ring marks their first meeting. Jun offers to buy Ryuji's late father's boxing gloves, an act conveying dismissiveness toward Ryuji's potential that sparks their rivalry and motivates Ryuji to pursue boxing seriously.

Jun's privileged background stems from being the favored twin in the Kenzaki family, designated sole heir to the fortune. This led to separation from his brother Jun Shadow during infancy and fostered childhood arrogance, evident when he forcibly takes Ryuji's gloves and throws money at him. His early boxing career showcases natural talent, earning him the monikers "Superstar" and "Genius."

Throughout the series, Jun maintains a proud and competitive personality. He primarily acknowledges only Ryuji as a worthy rival, showing selective respect amidst general condescension. Moments of emotional vulnerability surface, such as mourning Takeshi Kawai's sacrifice during an international tournament and expressing concern for Jun Shadow after their confrontation. His relationship with Kiku Takane evolves into marriage, resulting in a son named Rindo Kenzaki.

In competition, Jun demonstrates exceptional skill. His signature techniques, the Galactica Magnum and Galactica Phantom, reflect a fighting style emphasizing speed and precision, often leading to quick victories. During global tournaments, he faces formidable opponents like Führer Skörpion and Theseus, acknowledging their near-equal prowess—a rare admission from his typically self-assured character.

Jun's later life involves mentoring the next generation. After he and Kiku die, their son Rindo is raised by their teammate Ishimatsu Katori, continuing the boxing legacy in the sequel series *Ring ni Kakero 2*.