Just as Kurogane Ren was about to retrieve the meteorite, he suddenly paused.
He raised a hand and rubbed his forehead, as if trying to ease a headache.
It wasn't due to any illness. Rather, one of his shadow clones—responsible for experimenting with the Ghost Bud Technique to fuse a second body—had just dispelled, flooding his mind with a surge of accumulated memories.
He had specifically instructed that clone not to experiment for too long. Otherwise, the overload of incoming memories might become too much for him to handle at once.
Normally, his shadow clones would dispel themselves after a certain period for this very reason.
After organizing the influx of memories, Kurogane Ren formed hand seals again and created another shadow clone. Without hesitation, it headed straight into the laboratory.
Watching it leave, he reflected that this wasn't his only clone. Two others were currently practicing ninjutsu.
Compared to experimentation, practicing techniques was much easier to handle. Most of it was repetitive work with little memorable detail. Even after dispersal, the mental burden was minimal—unless, of course, he created hundreds of clones at once like Naruto.
Once the clone disappeared from sight, Kurogane Ren let out a quiet sigh. His current strength still didn't allow him even a moment of relaxation. There were too many things he needed to do—train techniques, acquire knowledge, conduct experiments.
Compared to before he obtained the Ghost Bud Technique, his workload had only increased.
A troublesome kind of happiness, he thought.
Having clear goals and meaningful work, even exhaustion felt rewarding as long as there were results.
As the original body, he didn't remain idle either. He retrieved the meteorite from the cultivation tank, thought for a moment, then sat down cross-legged with it resting in his palms, beginning to absorb its activity and convert it into star chakra.
If the Star ninja had seen this method, they would have been utterly stunned.
They would never dare train like this. Even someone as talented as Natsuhi would likely be killed by the meteorite's radiation before completing such a process.
Kurogane Ren, however, relied on his Uzumaki bloodline to endure it head-on.
Naturally, this made his cultivation speed extremely fast.
…
Several days later.
Kurogane Ren examined the chakra within his body. Though not fully refined yet, it had already taken shape.
He formed a Rasengan in his hand, but this one was different. A faint purple hue lingered within it.
Without hesitation, he slammed it into a stone wall.
The moment it made contact, a burst of light erupted—white mixed with traces of violet.
When everything settled, a massive crater had formed in the wall.
Kurogane Ren studied it and nodded. The power had increased by roughly twenty to thirty percent. And this was before completing the full refinement. Once fully stabilized, the increase would likely reach around fifty percent.
While it couldn't compare to tailed beast chakra, it was still a significant enhancement.
But the experiment wasn't over.
Chakra surged in his palm once again, forming another sphere. At first glance, it resembled a Rasengan, but the sharp, piercing sound and its shuriken-like shape made it clear—
This was not a Rasengan.
It was Wind Release: Rasengan.
Unlike the smooth sphere of a normal Rasengan or the massive form of a Rasenshuriken, this version was only slightly larger than a standard shuriken.
This was the result of his shadow clones' training—he had successfully mastered Wind Release: Rasengan.
From here, he was not far from achieving the Rasenshuriken. All that remained was increasing the chakra output and stabilizing it further.
But stabilizing such immense chakra wasn't easy. Recklessly increasing the output without proper control would lead to an incomplete technique, like Naruto's early Rasenshuriken, which required close-range use.
The result would be devastating to both enemy and user.
If Kurogane Ren wanted to use Rasenshuriken safely without Sage Mode, he would have to perfect its stability to the point where he could throw it freely without consequences.
He dispelled the Wind Release: Rasengan. While its backlash wasn't nearly as severe as Rasenshuriken's, it still existed.
For that reason, it was better to leave such techniques to shadow clones whenever possible.
As for why clones couldn't use Rasenshuriken?
Simple—they didn't have enough chakra.
Even Wind Release: Rasengan consumed a considerable amount. Rasenshuriken required far more.
Even at full power, Kurogane Ren estimated he could only use it two or three times, and that was thanks to his Uzumaki bloodline.
If he wanted his clones to use it, he would have to replicate Naruto's method—having the original body supply chakra while the clone shaped the technique.
Even Naruto, when he used Rasenshuriken against Kakuzu, could only manage three uses before becoming severely fatigued, and that was with his already massive reserves.
In Sage Mode, Naruto could use two Senjutsu-enhanced Rasenshuriken, though that was limited by the duration of Sage Mode itself.
Factoring in his exhaustion after using the Massive Rasengan, it could be inferred that even at full strength, without Sage Mode, Naruto likely couldn't produce more than ten Rasenshuriken.
And that didn't even include Nine-Tails chakra.
It was clear that, even with a defined training method, very few people could actually use this technique.
Chakra capacity alone eliminated the vast majority.
"I still need more chakra," Kurogane Ren muttered.
With his Uzumaki bloodline, further increasing his chakra through other bloodlines would be difficult. Even if possible, the improvement would be minimal.
That left only one option—
Physical training.
He had tried taijutsu training before, but his natural physical aptitude had been lacking, so he had abandoned it. Now, with his Uzumaki vitality, he could begin training using Might Guy's methods—though he couldn't start at such extreme levels right away.
And physical training couldn't be delegated to shadow clones.
Clones would only transfer fatigue and experience back to him. But true physical conditioning required repeated tempering of the actual body. Experience alone was meaningless.
There were no shortcuts.
At that thought, Kurogane Ren rubbed his temples again, a faint headache returning.
His workload had just increased once more.