Hunter x Hunter: Phantom Rouge.

One day, Kurapika spots a child who looks very similar to his childhood friend, Pyro. However, when he catches up to him, the boy steals Kurapika's eyes with some kind of magical power. Gon, Leorio, and Killua promise to help find who took his eyes and get them back, but Killua is having his own problems when he is forced to face his past and whether he really is worthy to have Gon as a friend.