He is a prominent fighter in the Heavens Arena and an apparent celebrity. Lives on the 200th floor as a fighter, uses martial arts and is very skillful in hand-to-hand combat. He had accumulated enough wins to become a Floor Master.

Two years ago, Kastro was defeated by Hisoka in the Heavens Arena making it his only loss. After this, he trains rigorously to improve his Nen and gains nine wins and then challenges Hisoka for his tenth.