Lightning

Immediately before he slammed into the ground, the other boy disappeared
from his field of view. Itachi took a sharp breath. He hadn’t felt a hint of
movement in Nemui. His action was too sudden. He hadn’t seemed to be
shifting his weight to either side.

He had been slow to anticipate his opponent’s movement. In that
momentary opening, Nemui had gotten the jump on Itachi.
He heard a snore from behind.

Thunder ... Itachi immediately tumbled forward in a basic somersault, and the right
arm brandished by the sleeping Nemui grazed the front of his face. The arm
pushed past him with incredible force, white electricity turning into countless
bolts of lightning, enveloping the arm.
So is that the true form of lightning, Itachi wondered absently as he landed,
getting some distance from his opponent.

Book of Bright Light Chapter 3 Part 1