After he heard Obito's comment, Itachi knew what was coming. He dropped down, almost straight down as he jumped from branch to branch, then dove through a thick tangle feet first and his arms under his shin to protect his face from the worst of the scratches. Itachi then went careening to the right and into thicker foliage, which he had no issues plunging through. He'd grown up getting slapped in the face by branches.

He was also still smaller than Obito, and could slither through branches where his cousin couldn't, which was exactly what he intended to do. Of course, he couldn't do that all of the time, but an erratic movement pattern and thicker foliage would hopefully keep Obito from catching him.