He is a distinguished fighter in the Heavens Arena and a notable celebrity. Living on the 200th floor as a fighter, he excels in martial arts and hand-to-hand combat, having accumulated enough victories to become a Floor Master.
Two years ago, Kastro suffered his only defeat at the hands of Hisoka in the Heavens Arena. Following this loss, he trained rigorously to enhance his Nen abilities, securing nine consecutive wins before challenging Hisoka for his tenth.
Kastro challenges Hisoka to a rematch. Although he is naturally an Enhancer, Kastro's "Doppelganger" ability relies heavily on Conjuration and Manipulation, fields in which an Enhancer can achieve a maximum proficiency of only about 60%. This makes his ability difficult to use and requires significant Nen energy and concentration.
Despite these challenges, Kastro combines his Conjuration and Manipulation abilities to compensate for the weaknesses of his doppelganger, creating a lethal combination. However, Hisoka exploits Kastro's vulnerabilities, distracting him with his own abilities, and ultimately kills him.
