Gon couldn't handle the pressure of seeing Kite's body so he runs away. Killua followed him, so as Knuckles and Shoot. He hides in a cave where a mystical accident happens and the four hunters are teleported to a new world full of people who call themselves Benders. While there they will help the young Avatar Aang find his destiny as Avatar while also find a way back home.

At the end of the final battle with Killua and Illumi, Illumi throws his little brother into a dark abyss almost killing Killua. With no way out a mysterious force transports him to the avatar world. By making a wish to be free of the grasp of his family, going on a journey again after Gon parted ways, meeting new people, and becoming stronger. Kill ends up with the avatar group.

The next in the cycle is earth. That's where Gon Freeccss comes in! (set in the world of avatar and before gon, killua, kurapika and leorio have met.)