On the training ground, Kakashi transformed into a bolt of lightning, darting back and forth as he launched continuous charges toward Nico Robin.
In addition to improving Kakashi's physical fitness, the Lightning Release Body Refining Technique was also subtly increasing his resistance to and control over Lightning Release. The improvement of these two abilities meant that by using the standard cell stimulation method, Kakashi could withstand more Chakra and burst with even greater speed.
If Kakashi, transformed into lightning, was considered a high-speed, high-agility assassin, then Nico Robin, standing opposite him, was a mage who had mastered multi-casting!
Dozens of arms grew from Nico Robin's back, each hand forming a different hand seal, giving her a visual resemblance to the Thousand-Armed Guanyin.
With so many hands forming seals at high speed simultaneously, the speed at which Nico Robin performed Ice Release Ninjutsu was beyond imagination. Casting three to five Ninjutsu at once was enough to catch any Ninja opponent completely off guard.
Ice Release: Tearing Ice Crystal Wall, Ice Release: Swallow Snow Storm, Ice Release: Breaking Dragon Fierce Tiger... One Ice Release Ninjutsu after another forced Kakashi to constantly dodge Robin's attacks, and the summoned ice walls made Kakashi's attacks almost entirely ineffective.
Even though it took less than a second for Kakashi to shatter an ice wall with his current strength, Robin could summon two or three more in that same amount of time.
"Miss Nico Robin, isn't your Chakra amount a bit too abnormal? Even the Kage of the Five Great Ninja Villages can't squander Chakra like you do."
Retreating from Robin's attack range at extreme speed, Kakashi spoke with a troubled expression, panting as he complained.
Since the battle started, his opponent had thrown out at least dozens of B-rank and C-rank Ice Release Ninjutsu. Logically, even a Jonin-level Ninja would have nearly exhausted their Chakra after using so many techniques.
However, the Chakra in Nico Robin's body was at least ten times that of an average Jonin. Furthermore, as someone from the One Piece World, not only did her physical stamina far exceed the Ninjas of this world, but her recovery rate was also much stronger.
In the One Piece World, even an ordinary person can recover in a few days after a near-fatal injury just by applying bandages and eating and drinking well. In terms of Chakra, this meant Nico Robin's Chakra recovery speed was also more than ten times faster than that of an average Ninja.
Robin could fully recover the Chakra spent on an attack of that intensity in less than five minutes, so the pressure on her was nowhere near as great as Kakashi thought.
"Is that so? It's probably just that your Chakra is too scarce. Kakashi, you should train more. Otherwise, being so weak at such a young age would be truly pitiful."
The mischievous Nico Robin responded to Kakashi with a smile on her face.
Kakashi's face darkened slightly. At only thirteen or fourteen, he wasn't yet the thick-skinned, decadent Ninja who would openly carry adult novels to test his students over a decade later. He still cared a bit when someone called him weak.
"Alright, it seems the results of this test were very successful. Kakashi, you've also become quite a bit stronger!"
Standing to the side, Vegapunk, who was staring at a device analyzing the battle data of the two, closed the instrument in his hand and showed a smile:
"From the battle just now, Robin, you've become familiar with your new fighting style. If you combine it with the restrictive abilities of the Flower-Flower Fruit, there probably aren't many people in this world who can be your match."
"As for Kakashi, your speed has increased by about 13%, and your Chakra volume has increased by fifty percent. Although the rapid progress is partly because you just started training, based on this estimate, the Lightning Release Body Refining Technique can increase your Chakra by at least twofold and your speed by about twenty-five to thirty percent."
This effect was already staggering. Although for a Ninja, the amount of Chakra is not the sole factor determining their combat power, it is an important one. Especially for someone like Kakashi, who was originally lacking in 'mana,' doubling his Chakra could significantly enhance his strength.
Because of this, Kakashi's expression improved considerably, and he stopped dwelling on the issue of Vegapunk using him as a test subject. Most importantly, there was no point in pursuing it—none of the trio before him were simple characters. If they got serious, even the weakest, Nico Robin, could easily suppress him.
For the three currently in the remote Land of Snow, Konohagakure held no deterrent power. Even though Kakashi had been gone for so long, Konohagakure hadn't sent anyone to investigate, showing that even the strongest Ninja village had places beyond its reach.
After all, the distance was so great, and they were separated by the Land of Water. By the time Konohagakure fully reacted, it would probably take one or two months, and taking specific action would likely take even longer.
This was only because Kakashi was a relatively important figure. If it were any other ordinary Chunin, Konohagakure probably wouldn't even send anyone to investigate such a backwater place like the Land of Snow.
However, Vegapunk estimated that it wouldn't be long before Konoha came knocking. In other words, he wouldn't be able to use this handy tool of a person, Kakashi, for much longer.
After finishing the combat analysis, Vegapunk took out another nutrient solution and handed it to Kakashi.
Since Kakashi began practicing the Lightning Release Body Refining Technique during this period, Vegapunk's supply of nutrient solutions had never ceased. Kakashi didn't have much suspicion about this; secret medicines existed in the Naruto World, and high-energy nutrient solutions with special effects were not uncommon.
Seeing Kakashi drain the nutrient solution in one gulp and sensing that the Nanoparticles controlled by the quantum brain had spread throughout Kakashi's entire body, a trace of a smile appeared at the corner of Vegapunk's mouth.
In the Naruto World, the various methods Vegapunk had developed in the One Piece World to control people were no longer very effective.
For example, bombs implanted in the brain could not be hidden from the Byakugan, and brainwashing using the quantum brain was difficult to hide from Ninjas who possessed Chakra. Cloning was still effective for ordinary people, but for Ninjas with Chakra, the clones were significantly inferior to the original.
The extraordinary power of Chakra was not only related to the physical body but also had a certain connection to the spirit. Even for clones, the nature of their Chakra differed from the original.
To this end, Vegapunk had recently used the power of the quantum brain, his own Observation Haki, the laboratory instruments, and his ability to control magnetic fields and electric currents to finally manufacture a batch of miniature Nanorobots.
These Nanorobots were tiny individuals. Once they entered a human body, even abilities like the Byakugan could not detect them. Controlled by the Quantum chip in Vegapunk's brain, they could perfectly serve as a hidden means to control others.