Sasuke barely blocked the blow with everything he had

"He left. What a shame. He was pretty strong, too. But it doesn't matter. We still have a backup plan for Sasuke," Kimimaro said calmly.

"What backup plan?" Lee asked, immediately dropping into a fighting stance.

"Oh, you don't need to worry about that," the white-haired ninja said, launching an attack at the green-clad Lee.

Meanwhile, Naruto

Naruto chased Sasuke with everything he had, finally catching up to him at the Valley of the End. Sasuke stood atop the head of Madara Uchiha's stone statue.

"Where do you think you're going?" Naruto shouted, finally bringing Sasuke to a halt.

"Heh, you're still trying to stop me, dead last?" Sasuke turned around, his face full of scorn.

"Of course I am. Sasuke, what's gotten into you? You sold yourself to Orochimaru just for revenge? All he wants is your body! That's all he's ever wanted!" Naruto desperately tried to bring the wayward Uchiha to his senses.

"What do you know? You've never lost someone you loved! You've never suffered the pain of having your entire family slaughtered in a single night! You don't understand me at all, because you've never had anything to lose!" Sasuke roared hysterically.

"Fine. If you won't listen, I'll just have to drag you back by force," Naruto said gravely.

"Heh, you can try. But this fight won't be anything like the one at the hospital." As he spoke, Sasuke activated the first stage of his Cursed Seal.

"Heh, using the Cursed Seal already? Figures. Only trash like you would go running to a pedophile, relying on the scraps of filthy power he gives you to comfort yourself and pretend you're special." Naruto sneered, took a fighting stance, and charged.

The two instantly clashed. The strength boost from the Cursed Seal, combined with the Sharingan's predictive ability, actually allowed Sasuke to keep up with Naruto's superhuman speed in direct combat. Every time Naruto landed a punch, Sasuke immediately struck back. Anyone watching could tell that neither of them would walk away from this fight unscathed.

"Damn you, Naruto! Fire Release: Great Fireball Technique!" Sasuke bellowed, sending an enormous fireball hurtling toward Naruto. Naruto narrowly dodged it, then quickly formed hand seals and fired a wind bullet into the Uchiha's flank, blasting him off the cliff.

Naruto thought, From now on, I can't use Wind Release unless I'm absolutely sure it'll work. If I get the timing wrong, his Fire Release will feed off my Wind Release and explode right in my face. Then I'll end up in a burn ward.

Damn that dead last. Even with the Cursed Seal active, all I can manage is a draw? He's going to pay for this. Damn you, Naruto! Sasuke thought through gritted teeth.

The battle continued, every collision between the two boys tearing apart the valley. The Cursed Seal made Sasuke far stronger than Naruto, allowing every blow he landed to inflict greater damage.

Sasuke slammed an Axe Kick into Naruto, sending him crashing to the foot of the waterfall. Standing high above him, Sasuke looked down with a smug, vicious grin.

"See that, dead last? This is why I'm leaving. With this power, I'm far stronger than you, and this is only the Cursed Seal's first stage. What good is staying in Konoha? Orochimaru can give me more-so much more! With this power, I can take revenge on Itachi! And this is only the first stage!" Sasuke laughed wildly.

Naruto thought, This is ridiculous. The Sharingan and the Cursed Seal are too much together. Neither one scares me on its own, but combined, the Cursed Seal's physical boost lets him see and counter everything I do. My speed and unpredictable fighting style are practically useless now. The only trump cards I have left are the Rasengan and the Nine-Tails' chakra. But even if he'll probably be executed when he goes back, or at least locked up for life, I still don't want to kill the bastard.

He looked up at his black-haired opponent, his mind racing.

Sasuke quickly formed three familiar hand seals. A Chidori gathered in his palm, and he charged down the waterfall's rock face, picking up speed.

Damn it, he's using the fall down the waterfall to accelerate. He's too fast! I have to counter now! Naruto thought, instantly forming a Rasengan in his palm.

"Chidori!"

"Rasengan!"

The two powerful ninjutsu collided with a thunderous crash. Suspended in midair, the two boys poured everything they had into overpowering each other's technique. Then an earth-shattering explosion blasted them both away, slamming them into the rock walls opposite them.

Naruto struggled to his feet and looked around, but Sasuke was nowhere in sight. Damn it, where is he?

"Behind you, dead last!" Sasuke roared. Naruto instantly felt a terrifying burst of chakra.

Sasuke stood right behind Naruto, the Chidori in his palm ready to strike. Naruto had no time to dodge. The red-eyed Uchiha drove his hand straight through the right side of his chest.

Naruto coughed up a mouthful of blood, yet remained standing. As he looked at Sasuke's smug, triumphant smile, the wound in his chest felt nothing like the pain in his heart.

"See? I told you. In the end, you're just worthless trash without a clan. Only an Uchiha can defeat an Uchiha." Sneering, Sasuke turned and walked away without deactivating his Cursed Seal.

Inside Naruto's mind

"Unforgivable! I refuse to let some arrogant Uchiha brat treat me like a weak, worthless fool!" Enraged, the Nine-Tails poured out his chakra in a wild torrent. In the real world, Sasuke's betrayal had utterly infuriated Naruto, and he instinctively began drawing on the Nine-Tails' chakra in enormous quantities.

In the real world

Sasuke was about to leave the valley when he felt a terrifying surge of chakra unlike anything he had ever experienced. Even Orochimaru's chakra, which he had felt in the Forest of Death, was insignificant beside this power.

He whipped around and saw Naruto enveloped in a crimson Chakra Cloak. The wound in his chest healed at a speed visible to the naked eye, leaving not even a scar.

What is this power? Naruto, what the hell are you? A monster? I've never felt this red chakra before! Shock filled Sasuke's mind as he watched the blond boy he had just utterly defeated rise again. Only the fist-sized hole running through the front and back of his clothing remained over his chest, proof that the Chidori had struck home.

"Sasuke, this ends here. Even if I have to break every bone in your body, I'm taking you back to Konoha." Naruto spoke, but his voice sounded nothing like it normally did. It was eerily hoarse, like that of a demon from hell.

Fox ears and a single tail made of chakra slowly took shape on his Demon Fox Cloak. As Naruto's anger grew, the tail lashed wildly from side to side, and his power surged.

Sasuke stumbled backward, utterly at a loss as to how to handle this sudden change. In the end, he decided to strike first.

Naruto charged in an instant, moving several times faster than before. Sasuke threw everything he had into defending and only barely blocked the blow.