Naoya Okubo is a mixed martial artist and the absolute champion of the Ultimate Fight promotion, the largest mixed martial arts organization in the world. Born on November 4, he is thirty-two years old, stands 195 centimeters tall, and weighs 116 kilograms. He represents Muji Television as their affiliated fighter in the Kengan Annihilation Tournament. Known as the King of Combat and occasionally referred to as the Osaka Rocky, Okubo holds an undefeated record of twenty-six wins and zero losses in his promotion, with twenty-seven wins and zero losses reported in some sources, making him the first Japanese heavyweight champion in that organization. His background in combat sports began in childhood, where he was a promising baseball player. In high school, he was scouted for wrestling due to his physical build and went on to win the All-Japan championships. He then switched to amateur boxing and became an Olympic training candidate before transitioning to mixed martial arts, where he reached the top of the heavyweight division. Despite appearing to have left wrestling and grappling behind, he secretly continued training in those disciplines for nearly twenty years, a testament to his relentless work ethic. Outside of fighting, Okubo is easygoing, friendly, and approachable, able to socialize with even the most eccentric and dangerous fighters in the underground world. He enjoys gambling, has an eye for women, and carries a playful, sometimes boastful demeanor typical of his Osaka roots. However, he is also a cultured individual who appreciates shogi and enka music, and he takes martial arts with utmost seriousness, analyzing fights with sharp observation. His core motivation is to prove that the techniques of public mixed martial arts are effective against the secretive, martial-art-based fighters of the Kengan matches, serving as a bridge between the surface fighting world and the underground. In the Kengan Annihilation Tournament, he faced Kanoh Agito, the fifth Fang of Metsudo, in the first round. Okubo initially dominated the match by employing his signature fighting style, known as Composite, which seamlessly blends striking, throwing, grappling, and submissions into a fluid and unpredictable offense. However, Agito adapted by learning and replicating the Composite style, ultimately defeating Okubo with a strike to the temple. Although eliminated early, Okubo earned the respect of top fighters such as Kuroki Gensai and Raian Kure, who acknowledged his strength. This loss became a turning point for him, deepening his resolve. In the sequel series Kengan Omega, he competes for the Kengan Association in the team tournament against Purgatory, where he defeats the masked fighter Terashi by overwhelming him with fundamental techniques. Later, he participates in the Real Championship Tournament and loses to the rising star Justin Kitagawa in a hard-fought battle. Key relationships include his rivalry with Kanoh Agito, whom he views as a benchmark for his own growth; his friendship with professional wrestler Jun Sekibayashi, with whom he shares a mutual respect after a friendly match; and his camaraderie with fellow fighters Rihito, Himuro, and Kengan, who form a loose group that provides some lightness in the high-stakes world of Kengan matches. Throughout his appearances, Okubo develops from an undefeated public champion into a fighter who learns from defeat, refines his skills, and continues to challenge himself against increasingly powerful opponents. His most notable ability is the Composite technique, resulting from years of building fundamental skill in every range of combat. He also possesses a technique called the Golden Eight Seconds, where he stops his breathing and conscious thought for eight seconds to fight purely on reflex, allowing for maximum speed but leaving him heavily fatigued afterward. His grappling and wrestling foundations are among the highest in the Kengan tournament, and his technical precision across all areas makes him a versatile and dangerous opponent even against elite underground fighters.