"Shinra Tensei!"
Uchiha Itachi reacted quickly enough. On instinct, he used the most suitable ability, sending invisible repulsive force toward Naruto's body.
But Naruto Uzumaki was changing as well. Though he was only a child who had yet to graduate from the Ninja Academy and possessed no combat skills whatsoever, with the Nine-Tails' full support, his strength was no weaker than that of any adult ninja—perhaps even far greater.
A Tailed Beast cloak formed from the Nine-Tails' chakra had already covered his body. With the Nine-Tails' help, Naruto actually managed to temporarily withstand Shinra Tensei's repulsive force.
Uchiha Itachi was familiar with such a situation, because he had done it before himself. Of course, that had only been barely possible after activating Susanoo.
He also knew what he needed to do next: evade, or invest more chakra and strengthen Shinra Tensei.
His combat instincts told him that now was the time to dodge Naruto's attack, then use Banshō Ten'in or Chibaku Tensei to restrain Naruto, while leaving himself enough time to react to the Third Hokage's impending attack.
Yet he still chose to pour out more chakra, expanding both the range and power of Shinra Tensei. The suddenly intensified repulsive force finally sent Naruto flying.
"Kid! Run!" the Nine-Tails shouted the instant Naruto was blasted away by Shinra Tensei.
But although Naruto had just followed its advice completely, he ignored it now. He stomped hard against the ground and tried to charge at Itachi again, but only lunged forward a short distance before falling to the ground.
As he delved deeper into the use of the Rinnegan, Itachi finally understood why Pain, controlled by Nagato, had called himself a God. It was difficult not to become intoxicated by such power.
"Kou, you shouldn't have come..." the Third Hokage said anxiously.