After dinner, Haruto Kamiya returned to his room and pulled out the book on chakra extraction. To be honest, he hadn't studied this seriously even in his previous life.
He already had a basic understanding of chakra, though he didn't know the specific extraction methods. He had once asked Nina to teach him, but she admitted that although she could still use chakra, the theoretical knowledge had long been forgotten. Moreover, she didn't recommend extracting chakra before age six, as it could affect the body.
Haruto had also thought deeply about chakra. Chakra was a combination of physical energy and spiritual energy. Extracting it would certainly influence the body.
Spiritual energy determined how much chakra could be extracted in one attempt, while physical energy determined the maximum chakra reserve. Only after spiritual energy extracted and combined with physical energy could chakra be used.
To Haruto, physical energy was affected by both physical conditioning and bloodline. Physical strength could be trained, but bloodline was basically fixed.
Ordinary people had low bloodline coefficients, meaning they needed extremely strong physical conditioning to accumulate enough chakra. But bloodlines like the Uzumaki, for example, had a very high coefficient, which allowed them to possess enormous chakra reserves without being physically powerful.
Bloodline also subtly influenced recovery speed, though that mattered little in actual combat, since battles were usually decided within a few exchanges.
Haruto had wondered whether this world contained any treasures that could enhance bloodline coefficients, but after thinking it through, there seemed to be no such option. Hashirama cells? Haruto had no interest in turning himself into some half-human monster. He'd rather try to obtain a tailed beast than graft that kind of thing onto himself. But both options contradicted his goal.
Haruto wanted to grow as a human, in a human form, to reach the peak solely through human potential. Even if other forms were stronger, they didn't align with his path. If he were to become some monstrous fusion, he might as well follow behind the two main protagonists and ride their coattails instead.
Besides, Haruto didn't care that much. If he could grow stronger, great. If not… well, then he wouldn't. He'd accept it.
He sighed. The Naruto world lacked the convenient "heavenly treasures" seen in cultivation worlds. In those stories, some odd herb or crystal existed to boost foundational stats. Rare, yes, but they existed. In Naruto, such things simply didn't.
If such a treasure existed now, he would probably use it despite his ideals. Practical strength was more important than sentiment—at least while he was still weak. But if he were already powerful, he would refuse such things on principle.
After reading for some time and letting his food settle, Haruto closed the book.
"Mom, I'm heading out."
"Come back early, and be careful."
Nina was already used to Haruto going out to train daily. She had assumed he'd skip it today because of school, but apparently not.
He wasn't going out to play. Physical conditioning was the foundation of chakra reserves. Haruto refused to end up in situations where he ran out of chakra after only a few techniques.
Based on his self-evaluation, despite persistent training, his physical strength was roughly equivalent to an ordinary second-year academy student.
Recently, though, he'd felt notable improvement—likely age-related growth. With that in mind, he figured he could increase the intensity slightly.
Still, he had to test his limits carefully. It was fine to push his body, but not to drain it. He was still a six-year-old child. Strength training mattered, but so did ensuring proper development.
A few times of pushing his limits wouldn't hurt. Perhaps even breaking through his limit once could be beneficial.
Breaking limits wasn't terribly hard for him; he'd done it before. But that past attempt had left him feeling hollow and weak for days afterward—classic overexertion. Since then, he hadn't pushed to that degree.
Tonight, he decided to try again.
He arrived at an isolated training ground—and as expected, someone was already there.
He knew him well. Every time Haruto came, this boy was already training, and when Haruto left, the boy was still training.
Rock Lee.
A genius of effort. Haruto honestly felt Lee's body was something he couldn't keep up with. Theoretically, Haruto's potential limit might be higher, but human growth periods were limited. He might never reach that theoretical peak before adulthood.
Theory was theory. Reality was reality. For now, Haruto couldn't imagine surpassing Lee physically—and didn't plan to. He respected Lee's dedication.
"Oh! Haruto, you're thirty minutes late today! You must do extra sets!" Lee said, eyes lighting up like lanterns.
"Sure." Haruto didn't mind. He was already planning to test his limits.
Lee froze. Usually Haruto refused additional training.
Then Lee's eyes erupted with burning flames.
"Ohhhh! Haruto, you actually agreed! My youth is igniting! I shall reward myself with even more sets today!"
Haruto sighed. No matter how many times he saw Lee's theatrics, they were always a bit overwhelming.
They began training. Though they trained side-by-side, their routines were entirely different.
Haruto refused to use high-intensity workouts while still growing. He relied on lower intensity but longer duration—to steadily build foundational strength.
Time passed. Even with moderate intensity, Haruto was panting heavily, but he hadn't yet reached his goal. His body felt close to its limit, though mentally he was still holding on.
Lee watched, eyes misty with emotion.
Yes. This was youth.
Haruto's movements suddenly became smooth again. Lee recognized this phenomenon instantly. A second wind! Something he himself experienced often.
Lee shed actual tears.
"Such… such youth!"
Eventually, Haruto exhaled deeply.
"I did it." His limit was higher than expected—not a true limit, but the upper edge of what his current body could safely endure.
After cooling down with a bit more training, Haruto bid Lee goodbye and left with heavy steps. His body was exhausted but his mind was calm.
He would study more when he got home. He needed to master chakra extraction as soon as possible.
The next day, Haruto woke up surprisingly fine. Had his body improved that much? He pushed himself again.
On the third day—he crashed.
His body felt drained and sluggish, forcing him to stick to only basic exercises.
Apparently, breaking limits was possible—but not consecutively.
He'd need to calculate the ideal recovery window.
Haruto sighed.
Physical conditioning… chakra accumulation…
A long road lay ahead.