Like most people here (excluding Gon and Killua), Leorio will likely only be in the first couple episodes.

Leorio met Gon, Kill, and Kurapika at the hunter exam. The four of them have since been good companions checking in with each other and trying to help each other strive for their goals. Leorio hopes to make lots of money as a hunter so he can one day become a doctor. He wold never admit it to the others but he has this dream because he couldnt afford schooling for such a proffesion while his friend was sick, and he was to late seeing as his friend is dead and he is just now working as a hunter. He may seem like the calm and mature one of the group but he has a tendancy to snap, often at Kurapika who is truely the mature one (Though Kurapika has poor judgement in many situations.)