Hunter x Hunter (2011) - episode 50 - 06 Oct, 2012

The Phantom Troupe question Gon and Killua about the chain user, and that's when Killua realizes he could be Kurapika. Then they manage to escape and decide to find Kurapika and ask him to teach them more about Nen so they could fight against the Phantom Troupe. (Source: Wikipedia) Yorknew City arc/Phantom Troupe arc: (14/22)