Naruto's training continued in the form of taijutsu and chakra control exercises. Jiraiya gave technical instructions in the mornings while Naruto was bright and ripe with energy, and ended the days with backbreaking chakra manipulation sessions. Each day was more difficult than the last. By the tenth day, Naruto was using Kage Bunshin while sparring with Jiraiya's clone on the surface of the river, combining many elements of his training at once.
Jiraiya's clone ducked under a flying kunai as he countered a combo-attack from flanking Naruto clones. A Naruto clone hiding beneath the water's surface burst upward behind Jiraiya's clone, while two Narutos charged him from the front. Jiraiya's clone turned and grabbed the ambushing clone, and threw him at the oncoming clones, sending them all crashing into the water.
"Good use of the natural environment, and misdirection tactics," said Jiraiya's clone. "But you'll have to be faster than that."
They continued exchanging blows for several more minutes, pushing Naruto to the point of exhaustion, but Jiraiya's clone still managed to avoid any serious damage. Naruto's clones dissipated, and he laid out on the shore.
"Is that everything you have?" said Jiraiya. "Get back up."
Naruto struggled back to his feet. He started sinking immediately upon stepping back onto the water. Naruto attempted to conjure a shadow clone, but only produced a weak puff of smoke—he plunged into the river.
"I'm totally gassed, Pervy Sage," said Naruto as he strained himself crawling back to land.
"I told you not to call me that," growled Jiraiya. He shook his head. "You've barely begun to develop your full strength."
"We've been going nonstop for hours," said Naruto.
"You've tapped into much more chakra than this before, I'm sure of it," said Jiraiya. "What do you remember? How did you feel?"
"I don't know, I just sort of lost control," said Naruto. "I don't remember much, but it's only ever happened in intense situations. When there was a lot of danger."
"When was the last time you remember?" said Jiraiya.
"Not long ago," said Naruto. "In the Forest of Death we ran into this really strong guy named Orochimaru."
Jiraiya nearly flinched. So, it really was Orochimaru that put a seal on his chakra.
"I was scared," said Naruto. "And angry. It was something he said about Sasuke, I don't remember exactly."
"You were scared because you're weak," said Jiraiya. "You're too weak to protect yourself, and even worse, you're too weak to protect your friends."
"Give me a break!" said Naruto. "I'm getting stronger every day! What the hell do you know about anything?"
"I know about Orochimaru, that's what," said Jiraiya. "And I know your friend Sasuke is his target, and there's nothing you can do to stop him."
"Shut up!" said Naruto.
"I heard you want to be Hokage," said Jiraiya. "You don't have what it takes—not even close."
It wasn't a clone of Jiraiya this time, but Naruto charged in all the same. Jiraiya blocked a flurry of attacks before clocking Naruto with a swift elbow. Naruto staggered sideways, missing wide with a shuriken as he stumbled. Jiraiya knocked Naruto away with another blow.
"You said that danger brings out your dormant chakra," said Jiraiya. He vanished from Naruto's sight, appearing again in a split second to land a kick on Naruto's side. "Consider yourself in danger. Doton: Dark Swamp!"
Jiraiya performed a sequence of hand seals as he spoke, and Naruto began to sink into the earth underneath him as it morphed into viscous, chakra-imbued mud. He strained to break free, but Naruto's efforts were futile against Jiraiya's ninjutsu.
"Let me go!" said Naruto. "You're crushing me!" He was down to his chest in the quagmire.
"Escape on your own," said Jiraiya. "You could do it easily if you had control of your chakra."
The small bog continued to tighten, squeezing the air out of Naruto's lungs. He desperately tried to draw out more chakra, to fight the growing pressure, but he was on his last ounce of stamina and time was running out. Mud bubbled up around his neck and face, and with one final gasp for air he was consumed by the earth.
Jiraiya stared down at the dark patch of mud. Come on, Naruto. You can do this. As the seconds passed, Jiraiya prepared to release the ninjutsu. This was too much for him to handle so soon. He paused as he felt a powerful surge of chakra from underground, and the mud on the surface began to hiss and boil. The ground ripped apart, firing mud and rocks in all directions as Naruto burst forth. The blast of chakra produced a seismic quake, and reshaped the geography of the riverside as the hill crumbled, bringing a few trees with it into the water. Jiraiya leapt back, dodging chakra-scorched debris. Naruto was on all fours, lungs heaving, and cloaked in a layer of blistering chakra—a fiery tail of chakra waived behind him.
"Harness it!" said Jiraiya. Even with his relatively limited sensory talents, he could feel the dense, demonic chakra pulsing. "Focus your mind, Naruto!"
Naruto's pupils sharpened into thin slits. He let out a grating howl, and dashed toward Jiraiya with outstretched chakra claws. Jiraiya dove to the water, evading Naruto's savage attack by the smallest margin, his kimono shirt searing from the fluctuating cloak of chakra. Naruto chased Jiraiya onto the river, slashing down with an extending arm of chakra.
"Suiton: Water Wall!" said Jiraiya. A barrier of rushing water deflected the chakra slash with an explosion of steam. "Naruto! Calm yourself! Breath!"
Naruto felt a brief moment of clarity. He had a sudden awareness of his surroundings, and of the extraordinary chakra raging within him. It was dripping with malice, and far too powerful for Naruto to restrain. His body moved on it's own toward Jiraiya, but he was blinded with a smoke grenade as he approached.
"Suiton: Water Prison!" said Jiriaya as he blitzed Naruto from the side. Naruto was enveloped in crashing waves from all directions, wrapping around him and trapping him in a constricting sphere of water on the river's surface. As Naruto thrashed at his prison, Jiraiya performed a fuinjutsu sealing technique to quell the spreading demon chakra while it was still manageable. Naruto's chakra tail momentarily broke free of the water prison and connected with Jiraiya's shoulder, smashing him down into the water.
The effects of the fuinjutsu began suppressing Naruto's demon chakra, and Naruto's body went limp. He faded into darkness.