Half a month later, Kakashi Hatake and Sakura Haruno were discharged from the hospital. The jonin instructor decided it was time to check on the results of Naruto Uzumaki and Sasuke Uchiha's independent training.
On a Konoha training ground, the two boys were locked in a fierce battle. Every punch and kick was aggressive; they knew each other's strength too well to risk retreating and creating an opening.
With a resounding clash, they each landed a punch on the other, using the impact to push back and create some distance.
Naruto quickly formed a hand seal. "Ninja Art: Multi Shadow Clone Jutsu!"
Dozens of shadow clones instantly appeared around him, dispersing into formation and charging toward Sasuke.
Sasuke was not to be outdone. He formed a simple hand seal of his own and shouted, "Body Flicker Technique!"
Dozens of his own clones appeared, intercepting the shadow clones' assault. Against an ordinary ninja, the outcome would have been obvious—Sasuke's illusionary clones would be no match for shadow clones with physical bodies.
But as the two sets of clones clashed, puffs of smoke erupted across the training ground. Sasuke's technique was unique; he could use the Body Flicker to make any of his clones the real him in an instant. After one of his clones defeated a shadow clone, he would instantly swap positions, always changing where his real body was.
Seeing his clones defeated, Naruto smiled. "Ha, Sasuke, you finally mastered the Body Flicker Technique?"
"Yeah." Sasuke replied, a faint look of pride on his face. After more than half a month of work, he had finally done it.
After dispelling his clones, he drew a kunai from his tool pouch. "Not only that," he said in a deep voice, "I've also been working on the nin-taijutsu left by my brother Shisui... Uchiha Style: Halo Dance!"
Sasuke swung the kunai in a rapid arc, and three blades of fire erupted from the weapon, slashing toward Naruto.
A cyclone of chakra appeared in Naruto's palm. "Spiral Shield!"
The swirling energy rapidly expanded, forming a massive circular shield in front of him that blocked all three blades of fire.
Naruto dispelled the chakra shield and chuckled. "How about that? It's a failed jutsu, but it seems to work pretty well, doesn't it?"
"..."
The corner of Sasuke's mouth twitched. "Pretty well" was an understatement. He knew the power of his Halo Dance, yet Naruto's shield had blocked it easily. It was obvious that this "Spiral Shield" was an incredibly strong defensive ninjutsu. It could probably even defend against his Dragon Fire Technique.
Sasuke frowned. "It doesn't look like a failed product at all. Is it because it can only defend from the front?"
"No!" The chakra in Naruto's hand quickly re-condensed. The swirling mass flickered unstably for a moment before obediently transforming into a solid, white weapon in his palm.
Naruto held the weapon in a reverse grip and explained, "It's a failure because I've since developed the successful version... the Spiral Dance Umbrella!"
Ninjutsu that transformed chakra into a solid weapon was rare, and Naruto's Spiral Dance Umbrella was stranger still. The chakra composing it was in constant flow. If a small gap appeared in battle, the chakra would automatically replenish it, maintaining its form as if it were a living thing.
The tip of the weapon was extremely sharp, making it look more like a spear than an umbrella. Just from its shape, it was clear it wasn't something to be taken lightly.
Naruto had the Nine-Tails to thank for this development. It was only because Kurama had provided a portion of pure yin and yang chakra through the seal that Naruto had been able to learn how to condense yang-nature chakra.
Seeing Naruto proudly showing off the solid weapon he'd developed, the Nine-Tails, in the sealing space, covered its furry forehead with a paw.
"That idiot kid, he's gone down the wrong path again!"
The Nine-Tails had worried itself sick trying to get this kid on the right track. It had provided its chakra hoping Naruto would build on the principles of the Rasengan to create the ultimate jutsu: the Tailed Beast Bomb. The power of a Tailed Beast Bomb was undeniable.
But in the end, the little brat had only used the yang-nature chakra to develop a solid weapon. And why? Because Sasuke had been practicing his swordsmanship lately. This jinchuriki's brain really had a problem.
Since Naruto didn't have a weapon he felt comfortable with, he simply decided to create one he liked using concentrated chakra. He had originally wanted to make an iron rod, but he found he could incorporate the principles of the Rasengan into weapon development. This led him to create the Spiral Dance Umbrella—and its failed byproduct, the Spiral Shield.
These solid chakra weapons were composed of both wind and yang-nature chakra, making them incredibly sharp and hard.
Naruto heard the Nine-Tails' grumbling and his consciousness appeared in the mental space. "Kurama, don't curse me out in secret. You think I don't know what you're thinking?"
He continued, "I figured it out. My own chakra reserves can't support a Tailed Beast Bomb. I'd have to borrow your chakra to use it. And then you'd use that as an excuse, offering just enough chakra to make one, to try and trick me into opening the seal and letting you out, right?"
"..."
Hearing this, the Nine-Tails just lifted its claw, suppressed its anger, and muttered, "You really don't understand at all..."
"..."
Naruto's voice was low. "Last time, in the Hidden Hot Water Village, you told me you couldn't give me any chakra... But for the past few days, you've been secretly using your chakra to erode the seal every single day..."
The Nine-Tails lay down, not wanting to deal with him. Idiot kid, it thought. How can you compare then and now?
Ever since gaining Naruto's memories of a hundred years, it had only ever provided him with normal chakra, never again using the malicious energy that harmed his body.
It was all just karmic debt, it figured. All it could do was endure.
The Nine-Tails almost wished a powerful enemy would appear. Maybe then, in a desperate situation, Naruto would open the seal and finally understand its actions.
This Naruto was not obedient at all. The only good thing to come out of this time was that their relationship had eased slightly. As long as they didn't talk about undoing the seal, they could get along peacefully.
To make Naruto stronger, the Nine-Tails had to find a way to get him to undo the seal. However, because it had tricked him once before, Naruto wouldn't believe anything it said.
The Nine-Tails had even told Naruto its name, Kurama, trying to befriend him. But Naruto didn't appreciate the gesture and just assumed it was part of some new conspiracy.
What a mess.
Back on the training ground, Sakura was still stunned by her teammates' improvement. In just half a month, how had the gap between them grown so much wider?
Kakashi, however, was very satisfied with his two students' progress. He waved a hand at them. "Alright, Naruto, Sasuke, let's go. I'll treat you to ramen!"
-----
Bonus:
Nine-Tails: This is painful.
Naruto: What's your conspiracy now?
Nine-Tails: The Eight Gates. Why aren't you practicing it?
Naruto: That's pure taijutsu. If I focus only on that, what kind of loophole will you try to exploit?
Nine-Tails: Then what about the Tailed Beast Bomb I taught you?
Naruto: Can't practice it! If I do that, I'll run out of chakra, won't I?
Nine-Tails: You have a brain, kid, so why don't you use it correctly!
Naruto: Hmph! ╭(╯^╰)╮