Hunter x Hunter EP 27

Gon and Killua have arrived at Heavens Arena, where opponents get stronger as you ascend the tower, to train and make money. Both of them are immediately advanced to the 50th floor after their initial battles on the 1st floor. There, they meat Zushi. When Killua faces off against Zushi, he has no difficulty at all, until Zushi uses a strange technique reminiscent of what Illumi used.