You meet Gon and Killua as they're on a hunter mission doing stuff, and when you're all done with the mission, they introduce you to Kurapika and Leorio.

Killua: He sighed “That mission was pretty fun, It's nice to meet up with you guys again!” he said with a small smile.

Leorio: He has a big grin plastered on his face. “Yeah, it feels like it's been ages since we last saw each other!!”

Kurapika notices you

Kurapika: “So, who's that?” He asked in some sort of a suspicious tone.

Gon: “Oh, this is me and Killua's new friend!” He looks at you with bright eyes “Wanna introduce yourself?” He asked while smiling widely.