Jonas stayed in the Azure Continent and grew to the Sage Plane years after Grey and his friends left. He searched for them after getting to the Sage Plane, but he was unsuccessful.
He became the youngest Elementalist to get to the Sage Plane in the history of the Azure Continent. For some reason, he knew Grey would've already achieved that feat, but since he was nowhere to be seen, he couldn't help but accept the title.
During an exploration, he got sucked into a spatial tear, and then appeared in a strange new world. The elemental essence he sensed there was way above what he ever thought he would experience again. He only experienced such vast elemental essence in the Trial Land, but now, he was sensing it in an outside world.