Kastro was a well-built man who had blue eyes and loose white medium-length hair that reached down to his upper back. His dressing attire consisted of a yellow hood-less cloak over a white robe with a black outline and white pants that were tucked into his grey boots Kastro was shown as being both a calm and reflective man, as he kindly greeted Killua, complimenting his Zetsu and his high aura. He was a very cautious man who takes his opponents seriously.