Zushi

ズシ

A young boy who studies Shingen-Ryu Kung fu and Nen under the tutelage of Wing, whom Gon and Killua meet in the Heavens Arena. He is a formidable fighter and a prodigy in his own right, said to have skills only 1 out of 100,000 people have. However, he is quickly surpassed by Gon and Killua, who are said to have skills only 1 out of 10,000,000 people have. According to the results of his water divination, Zushi is a Manipulator.

(Source: Wikipedia)