At a secluded training ground
After using it briefly, Kakashi closed the mangekyō sharingan. However, even with such short usage, he could clearly feel that a significant amount of his chakra had been drained, along with a large portion of his yin chakra.
"No wonder the Kakashi in the original work nearly died from overusing the mangekyō sharingan," he murmured. "It's not just the depletion of chakra—his yin chakra must have been completely exhausted, causing him to faint and approach death."
Pulling down his headband to cover his sharingan, Kakashi touched his silver-white hair, a hint of helplessness on his face. Based on his current condition, he estimated that he could only use kamui once before collapsing from exhaustion.
Fortunately, this was just the beginning. With more practice, he believed he could eventually use it several times without fainting. As he aged, his chakra reserves and yin chakra would also grow, making him stronger.
However, another issue loomed. He couldn't afford to train with the mangekyō sharingan excessively because overuse would lead to blindness. Every activation was precious, rendering traditional practice impossible.
"Unless I acquire the eternal mangekyō or Hashirama's cells, I'll have to use it sparingly," he thought.
Since he had awakened the mangekyō sharingan, it had become his trump card. Even against a kage-level opponent, Kakashi was confident that, if they couldn't evade it, kamui would allow him to take their head.
The four symbols seal reappeared, fully sealing his sharingan. Once sealed, Kakashi felt his chakra replenished, surging through his body once more. Having used the four symbols seal numerous times, Kakashi had grown proficient at sealing and unsealing it instantly.
Under the moonlight, Kakashi unsheathed his millennium sword and stepped into the courtyard. He began practising with the blade, its movements fluid and graceful even without the use of chakra.
If someone observed closely, they would notice that Kakashi's sword style had diverged from the original Hatake techniques. His style was less aggressive and more flexible, emphasising adaptability over raw power.
As he moved, the sword's speed increased, creating afterimages and a sharp whistle as it sliced through the air. Under the moonlight, the scene was both captivating and exquisite.
The next morning, Kakashi arrived at Guy's home bright and early. Coincidentally, Guy was just stepping out of the door.
Seeing Kakashi, Guy's face lit up with excitement. "Kakashi! Your mission's over? Let's have a youthful showdown!"
Kakashi smiled and nodded. His reason for visiting Guy today was to train in taijutsu, but a match with him seemed like the perfect warm-up.
"Great! What's the challenge this time?" Guy asked eagerly.
Since the ninetails' attack, Kakashi had stopped avoiding Guy's challenges. Instead, he took them seriously, a change that made Guy surprisingly happy. Although Guy didn't know what had caused this shift, he decided not to question it.
"Let's race towards the seventh training ground," Kakashi suggested.
"Alright, let's go!" Guy yelled enthusiastically before sprinting off toward the training ground. Kakashi, still standing in place, sighed before following.
As they ran through the village in the early morning, the villagers couldn't help but notice the contrasting figures: Guy in green, laughing loudly like a madman, and Kakashi in black, lagging behind slightly, looking thoroughly embarrassed.
"Ah, my eternal rival! I'll pick up the pace now!" Guy shouted, increasing his speed.
Kakashi smirked. "Alright, but I won't fall behind."
The two arrived at the seventh training ground at nearly the same time.
"This is youth! A tie! Now let's start the match to settle the score!" Guy exclaimed before launching a punch at Kakashi.
Kakashi stopped, observing the punch. It was packed with power, and Kakashi was certain it would leave him bruised if it connected. He sidestepped, dodging effortlessly.
"Hey, Guy, you should wait for me to get ready before attacking," Kakashi said.
"Kakashi, enemies won't wait for you to get ready!" Guy retorted.
"Well, that's true," Kakashi admitted before adopting a fighting stance.
Guy didn't wait and immediately attempted a flying kick. Kakashi, realising Guy wouldn't hold back, began fighting in earnest.
"leaf hurricane!" Guy shouted as his kick whipped toward Kakashi.
Rather than dodging, Kakashi deflected Guy's leg to grab it and spun, throwing him a few metres away.
"Impressive! As expected of my eternal rival!" Guy praised as he steadied himself. "Now witness my leaf strong hurricane!"
Kakashi noticed a powerful kick heading straight for him. Reacting swiftly, he used shun-po and shunshin to vanish from sight.
Guy, confused, scanned his surroundings. "Where did you go, Kakashi? How can you disappear like that?"
Before Guy could react, Kakashi's voice sounded from behind him. "leaf village secret taijutsu: one thousand years of death!"
"What?!" Guy exclaimed, turning just in time to see Kakashi form a tiger hand seal before thrusting his fingers into Guy's backside.
"Aagh!" Guy yelped as he leapt into the air comically, clutching his rear.
Standing confidently, Kakashi examined his fingers with a sly smile. "This technique is really effective. As expected of a secret jutsu."
Guy, still wincing in pain, looked at Kakashi with awe. "Kakashi! What kind of taijutsu secret technique was that? I've never heard of it before, but it's incredibly powerful!"
"one thousand years of death," Kakashi replied.
"What a domineering name! Did you invent it yourself?"
"You could say that," Kakashi said casually.
"You truly are my eternal rival! This is youth! I must train harder to catch up!" Guy declared, his determination reigniting.
Kakashi sighed, rubbing the back of his head. "You don't need to be that excited, Guy."
But Guy was already lost in his world of youthful fervour, oblivious to Kakashi's exasperation.