After dinner, Kaito returned to his room, took out the book about chakra extraction, and started reading. To be honest, he hadn't studied this diligently even in his past life.
Kaito had a basic understanding of chakra—he just didn't know the specific method of extracting it. He had once hoped that Sinai could teach him, but unfortunately, Sinai said that although she could still use chakra, her knowledge of the specifics had long since been returned to her old teachers. Sinai also suggested that he shouldn't try to extract chakra before turning six, as it could have some negative effects on his body.
Kaito had thought a lot about chakra. Chakra is the combination of physical and spiritual energy, and extracting it must have an impact on the body.
Spiritual energy determined the amount of chakra that could be extracted at once, while physical energy determined the reserve. Only when physical energy was combined with spiritual energy could it become usable chakra.
Physical energy, as Kaito understood it, was influenced by both physical fitness and one's bloodline. Physical fitness could be improved, but bloodline was pretty much fixed.
Ordinary people had a low coefficient for their bloodline, meaning they needed to have a high level of physical fitness to have enough chakra reserves. But some bloodlines, like the Uzumaki bloodline, had a very high coefficient, which allowed them to have massive chakra reserves without needing a super-strong body.
And the influence of bloodline wasn't just limited to chakra reserves—it also affected recovery speed. However, this didn't matter much in actual battles, as fights were often decided in just a few exchanges, so a fast recovery rate wouldn't make much of a difference in one-off encounters.
Kaito had previously wondered whether there were any special herbs or rare resources in this world that could improve his bloodline coefficient. He'd thought about it and realized there probably weren't. The only thing that came to mind was Hashirama's cells, but Kaito had no interest in turning into some half-human, half-demon. If it came to that, he'd rather consider capturing a tailed beast, but none of that fit Kaito's goals.
What Kaito wanted was to grow as far as possible as a normal human, in human form. Even if other forms might be stronger, he was determined to take this path. So anything involving turning into a monster, like becoming a jinchuriki, didn't align with his goals.
If he had to turn into some sort of monstrosity, he might as well just stick close to the two main protagonists. All he needed was to be strong enough not to get treated as cannon fodder.
Kaito was quite laid back—if he could become stronger, that would be great, but if he couldn't... well, so be it.
After some time, Kaito realized there really weren't any rare resources in this world that could improve one's bloodline. Maybe there was something like the Dragon Vein, but Kaito couldn't remember when that appeared, and it probably didn't fit his goals anyway.
Kaito sighed. If only this were a cultivation world, there'd be all sorts of strange items to boost basic attributes. Though such items were often rare, it still felt better than having no options at all in the Naruto world.
Even if they were unlikely to be acquired, at least there'd be something to hope for. Here, everything relied on some random mutation of one's body.
If given the chance, Kaito knew he'd be tempted to use such things. Even if his heart wasn't in it, the logical choice was always to strengthen himself. But that was limited to his weaker stages—when he had no room to be picky.
If he grew stronger on his own and was then offered these things, he'd decline them. The problem was whether he'd be able to grow to that point.
After reading for a while, Kaito felt his dinner had settled a bit, so he closed the book.
"Mom, I'm heading out," he called.
"Come back soon, and stay safe."
Sinai was used to Kaito going out every day. She thought that maybe today, after his first day at school, he'd take a break, but it seemed like he was determined to head out again.
Playing was not on Kaito's agenda, though. Since chakra reserves depended on physical fitness, Kaito had decided not to slack off. He wanted to avoid running out of chakra after just a few jutsu in the future.
Kaito figured that, despite his consistent training, his physical fitness was probably only about on par with an average second-year student. He hadn't trained at a high intensity since he was still growing, but now that he was older, he felt like he could push himself a bit harder.
He thought it over: he needed to test this new intensity. It was fine to push his limits once or twice, but he was cautious not to overwork his young body. His body was still growing, and he needed energy for that growth. It would be foolish to sacrifice long-term gains for short-term improvement.
Still, a couple of times wouldn't hurt, and perhaps breaking his limit once might not be a bad idea.
As for breaking limits, it wasn't too difficult for Kaito. He'd tried it before, and it seemed related to the strength of his soul. The last time he had done it, his body had felt empty for days afterward, a clear sign that it had been too much. Since then, he hadn't pushed himself that hard again.
Now seemed like a good time to try it again. Kaito quietly made his way to a secluded training area, and as expected, someone else was already there.
That someone was Lee. Kaito was quite familiar with him by now. Whenever Kaito came here, Lee was already training. When Kaito left, Lee was still at it.
Yes, it was none other than Rock Lee, the hard-working genius. Kaito genuinely wondered how Lee's body could keep up with his level of training. If Kaito compared their training methods, he felt that his own theoretical potential was higher.
But that was only true assuming limitless growth. The problem was, human growth had its limits, and Kaito might not reach his theoretical potential before his growth period ended.
Theory was one thing, and reality was another. At present, Kaito couldn't see himself surpassing Lee in terms of physical conditioning, nor did he want to. He had immense respect for Lee's relentless effort.
"Oh, Kaito! You're half an hour late today. We'll have to do a few extra sets!" Lee's eyes lit up when he saw Kaito. Though Lee was used to training alone, having a companion always made him happier.
"Alright," Kaito said. He'd already decided to push his limits today, so adding a few more sets seemed perfect.
Lee looked stunned for a moment. Kaito had never agreed to extra sets before, and Lee's eyes seemed to light up with a burning flame.
"Oh~~~ Kaito, you actually agreed! This is it! This is youth! I've decided—I'll reward myself by doing a few extra sets today!"
Kaito couldn't help but smile awkwardly. Even though he'd seen it many times, he still thought Lee's enthusiasm was a bit over the top.
And so, today's training began. Kaito moved to the other side of Lee. Though they were in the same training area, their methods differed.
Kaito believed his body was still in the growth phase, so he refrained from doing high-intensity training. Instead, he focused on low-intensity exercises over longer periods to accumulate strength.
As time passed, Kaito became breathless, even with the low intensity. He hadn't yet reached his target for today. His body felt like it was approaching its limit, but mentally, he thought he could push on a bit more.
Seeing Kaito push himself, Lee was on the verge of tears. Truly, youth was igniting before his eyes!
In Lee's gaze, Kaito's movements suddenly regained their fluidity. Lee recognized this—it was a state he often reached himself, the embodiment of youth!
This time, Lee couldn't help shedding tears of inspiration.
"Phew, I did it." Kaito realized his limit was a bit higher than he'd expected. Though calling it a limit wasn't accurate—it was more of his body's current upper threshold.
After a bit more training, Kaito waved Lee goodbye and walked away with heavy steps. His body was exhausted, but his mind was clear. He decided he'd study more when he got home, aiming to learn how to extract chakra as soon as possible.
The next day, Kaito felt surprisingly good—had his physical capacity really improved so much? Encouraged, Kaito tried pushing his limits again.
Then, on the third day, Kaito hit his limit. His body was overwhelmed with fatigue, and he could only manage some basic exercises. It seemed he could push himself, but not continuously, and Kaito now understood the necessary interval between pushing his limits.
Kaito sighed. Physical conditioning and chakra accumulation—it was going to be a long road.