Kastro

A fighter in the 200th floor class of the Heavens Arena. An Enhancer. He reached the 200th floor class without knowing Nen, was baptized by Hisoka's Nen attack, and although he was defeated, he survived and awakened to Nen. Using the humiliation as motivation, he trained with the goal of defeating Hisoka. He was said to be the closest to becoming a Floor Master. He faced Hisoka again, initially fighting with the upper hand, but Hisoka saw through the flaws in his ability, leading to a brutal defeat. Hisoka described his defeat as "a waste of capacity (memory)," and Wing also criticized him for using the highly advanced Conjuration and Manipulation composite ability, Double, which was incompatible with his original Enhancer ability. In the first anime adaptation, his match with Hisoka was significantly shortened due to regulations.

Tiger Bite Fist

A martial art that attacks by mimicking a tiger's claws and fangs with both hands. The power increases when aura is gathered in both hands. Wing, the instructor, praised it as a technique that could make him the best user if mastered.

Double

An ability to conjure and manipulate one's own double. A highly advanced composite ability that involves "Conjuration," "Emission," and "Manipulation." Both the original and the double can use the Tiger Bite Fist, which Kastro named Tiger Bite True Fist. Kastro and the Double are indistinguishable and can be summoned or dismissed at will. If the opponent is unaware of the ability, a surprise attack is possible, and even after the ability is known, a numerical advantage can be created. However, it requires considerable concentration, and if he takes damage and loses focus, he cannot summon the Double, lacking sustained combat power. Additionally, although normally indistinguishable, since it reproduces his imagined (normal) appearance, it cannot replicate wounds or dirt acquired during battle, making it easy to see through as the fight progresses.