"What the fuck was that?" Kisame asked, once again looking over to Itachi.
Itachi's face, despite being mostly blank, held both shock and even the slightest hint of awe. "Impressive. Most impressive."
"Mind filling me in?"
"Naruto-kun is using no chakra for his technique," said Itachi.
"How is that possible?" Kisame demanded, the man completely taken aback. "If he's not using chakra, what is he using?"
Itachi continued. "Chakra consists of both physical and mental energy." His Sharingan eyes glinted. "Naruto-kun has succeeded in manifesting mental energy by itself."
Kisame's eyes widened, as Naruto gave a thin smile. "You've figured it out, as I would've expected, Itachi."
"How the hell do you only use mental energy?"
Itachi then did something very strange for him; he shrugged. "I am not the one who created this technique, Kisame. But my theory is that due to Naruto-kun's intelligence, he has considerably higher mental energy than the average shinobi."
"But unless his physical energy is negative, his mental energy can't be stronger than chakra," said Kisame.
"That would be the beauty of it," said Itachi. "Despite how much mental energy he has, it is still too weak to be manifested as anything other than movement. To be precise, vibrations. The vibrations pass through his body and to the earth."
"So what? He's creating earthquakes with his mind?"
Itachi nodded. "More or less."
Kisame looked back to Naruto. "Fuck."