Branches are so brittle, easy to slice, easy to put too much pressure on, easy to snap. Full of vibrancy until they fall, green leaves and all.
And while Jae-Ha can easily blend in among the branches with their dark green leaves, and his long, green hair, he made a bit of a miscalculation of Shin-Ah's eyesight, despite bearing witness to that very fact a couple days prior.
Just Shin-Ah could be so quiet, so Jae-Ha wasn't expecting him to reveal Jae-Ha's presence to the others. Just his efficiency in "uprooting" Jae-Ha from his hiding place within a tree, dropping Jae-Ha straight into an equally green bush is something to be commended. And so, a reintroduction was in order.
A new beginning couldn't begin within a tree's branches after all. And Jae-Ha clearly was going to be traveling with far more people than just Yona, a fact that was especially clear when he found a tree was not a far enough away hiding spot nor as hidden as he'd thought it would be.
But a new beginning with the other dragon warriors, Yun, Hak, and Yona didn't sound like a bad way to spend his time after all.