Cold, damp air.
This was the base of Root.
On either side of the stone corridor, torchlight was swallowed by darkness, illuminating only a small patch of floor.
A tall, slender figure in a hood and cloak moved silently through the corridor. His pale skin looked sickly in the dim light, and his golden, slit-pupiled eyes were as cold and sharp as a snake's.
It was Orochimaru.
Orochimaru had returned.
He pushed open the heavy stone door at the end. Inside, Shimura Danzō sat upright in his seat, like a statue fused with the shadows.
"Mission complete, Lord Danzō." Orochimaru's voice was characteristically hoarse and resonant, devoid of emotion.
"Thanks for your effort, Orochimaru." Danzō opened the eye not covered by bandages, his sharp gaze settling on Orochimaru. "As it happens, there have been some new developments in the village that need your attention."
"Oh?" Orochimaru ran his long tongue over his lips. "If you're personally involving yourself, I assume it's no simple matter."
Orochimaru watched Danzō, waiting for him to explain.
"A child. A very interesting child." Danzō concisely recounted the Cloud Village kidnapping incident and the subsequent graduation assessment, focusing in particular on Hiroki's performance.
Orochimaru listened in silence, not a ripple in his golden eyes.
He had heard and seen too much about so-called battle intelligence and quick decisions under pressure. None of it could stir the slightest emotion in him anymore.
Konoha had never lacked geniuses. Dan Katō was a genius, Nawaki was a genius, and there were countless others whose names he didn't even know. He had lost track of how many he'd met.
But no matter how gifted they were, they all met the same end.
And he was no longer young enough to feel stirred by so-called geniuses.
After all, death was the one thing he could never escape...
Orochimaru stared at Danzō, waiting for him to tell him what he was supposed to do next, what mission he was to carry out.
He had no interest in hearing about some little prodigy.
That was, until Danzō mentioned the crucial ability.
"...His Kekkei Genkai seems to let him read and copy another person's jutsu through physical contact alone."
"An even more extreme theory, based on the information we have, is that under certain conditions, he may be able to read someone's thoughts, memories, and jutsu without physical contact."
At last, a faint glimmer appeared in Orochimaru's eyes, like a snake sensing the warmth of prey in the dark.
Copy jutsu!?
The Uchiha could do that too. But reading minds and thoughts—wasn't that something only the Yamanaka Clan's secret techniques could accomplish? How had it become a Kekkei Genkai?
Orochimaru considered the matter with interest, but didn't let it show.
"Copy jutsu?" He chuckled, his voice tinged with disdain. "Sounds like an inferior version of the Uchiha Clan's Sharingan. What's the difference?"
The Sharingan—that was a masterpiece of a Kekkei Genkai.
All it took was a glance to turn an opponent's jutsu into your own.
An ability that required physical contact, on the other hand, was far too limited in a battle where everything could change in an instant.
Still, as a support ability, it was top-tier. Whether gathering information or copying another village's jutsu, it was exceptionally useful. No wonder Danzō had called him back early.
Danzō rose from the shadows and paced slowly. He gave a low, derisive chuckle. "The difference?"
With a hint of disgust, he sounded as if he were complaining, or perhaps scoffing. "The difference is that the Uchiha are the Uchiha. Konoha is Konoha."
He spoke each word deliberately. The implication made Orochimaru's gaze turn interested.
"And this child," Danzō turned around, his single eye fixed on Orochimaru, "is a blank slate. A blank slate we can shape however we please. He won't be restrained by family ties or swayed by those ridiculous, absurd emotions. A perfect blank slate. If we use him properly, he could... replace the Uchiha."
Replace the Uchiha.
So that was it.
But to be fair, the Uchiha Clan's emotions were indeed abnormal, and their minds were complicated. They were quick to anger and quick to act rashly, and they had no contact with anyone else in the village.
If the Uchiha left the village, there probably wouldn't be a single person in Konoha who'd be unhappy.
"So what do you think we should do with the boy?" Orochimaru smiled, dangerous light flashing in his golden eyes. "Where is he now? What do you need me to do?"
Danzō didn't answer. He simply tilted his head slightly toward the shadows in the corner.
As the leader of Root, he didn't have the time to keep tabs on a child who wasn't even a jonin, day and night.
There were more than enough things in and out of the village demanding his attention.
As for where Hiroki was, there were people whose job it was to answer that question.
Sure enough, the next moment, a masked Root shinobi dropped to one knee and reported in a flat voice. "Reporting to Lord Danzō. According to our continuous surveillance, the target, Sawada Hiroki, has stayed at home and kept to himself since the assessment ended. His most recent activity was... catching two mice in the back hills. He seems to be raising them."
"Raising mice?" Danzō froze.
Orochimaru froze too.
What kind of hobby was that?
Hadn't they been talking about copying jutsu? About reading minds?
Why had he started raising mice?
The answer was so absurd that it made no sense at all.
Orochimaru stared at Danzō in silence.
Danzō stared at Orochimaru in silence.
Neither of them said a word.
They seemed to be waiting to see who would crack first.
After all, a boy with such an unusual Kekkei Genkai, regarded with such high hopes by the leader of Root, had gotten some free time and decided to raise mice at home like a bored child?
But Orochimaru's hide clearly wasn't as thick as Danzō's. In the end, he was the first to speak. "If you want me to teach him, I may need to conduct a separate assessment of both of them first."
Orochimaru spoke softly. It might have sounded a little disrespectful to Danzō, but he really did suspect something had gone wrong with Root's intelligence network.
Danzō frowned, but didn't argue. Instead, he stared at the Root shinobi who had said Hiroki was playing with mice.
He, too, was beginning to doubt the reliability of this report.
"Squeak, squeak~"
At Hiroki's house.
Contrary to what Orochimaru and Danzō imagined, Hiroki really was playing with mice.
Don't ask why Hiroki hadn't used white mice, but had insisted on catching big rats. All he could say was that he'd wanted to catch some white mice in the back hills too, but the problem was, there weren't any!
So he'd had to settle for catching two rats as test subjects.
The good news—rats counted as computers too, and their file types were very similar to Hiroki's. The muscle-related sys files were almost identical.
The bad news—the results might have been a little too obvious. Far too obvious!
At that moment, two cages sat on Hiroki's desk. One held a big rat, and the other held a big rat too.
The cages were identical, but the rats inside them were very different.
A large gray-white rat was running furiously on its wheel in the cage on the left, moving so fast it was nearly a blur.
It was a whole size bigger than its counterpart in the cage beside it, which served as the "control group."
Even more horrifying, beneath its gray-white fur, bulging muscles rippled with explosive strength. Even its tiny veins were clearly visible. It looked like a bodybuilding champion rat, bred solely for combat and crawled straight out of hell.
The food bowl and water bottle in the cage were emptying at a visible rate.
Hiroki opened his logbook expressionlessly. In precise handwriting, it recorded the astonishing changes of the past week.
"Experiment log, day seven. Project codename: 'Pointy-headed Mouse.' Preliminary validation successful."
He looked at the "super rat," so full of energy it seemed ready to tear the cage apart, and felt like tossing his notebook aside.
In one week, it had gained a net 115 grams.
That number might mean nothing to most people, but Hiroki immediately pictured a more intuitive comparison.
The big rat weighed 407 grams and had gained a whopping 107 grams of muscle in a week. What did that even mean?
It was like an adult weighing sixty kilograms gaining fifteen and a half kilograms of pure muscle in a single week, without an ounce of fat.
Even if you had nine dragons pulling a coffin, like in the bodybuilding world's most extreme scenarios, you couldn't get that kind of result with all the hormones in the world!
This damn thing wasn't bodybuilding. It was Fengling Yueying!
His script was far more effective than he'd imagined!
Hiroki looked at his notebook, then at the rat on the other side, which was a whole size smaller. He was almost at a loss for words.
To be fair, before starting the experiment, Hiroki had expected to need a four-to-eight-week cycle to test his automated muscle-growth script.
But...
The power of the data still exceeded Hiroki's expectations.
Before discussing how much muscle the rat gained, we needed to understand how much muscle a rat could normally gain through training. Only then could we truly appreciate what Hiroki's script had accomplished.
First, the muscle repair and growth cycle was about three days.
After a person—or a rat—underwent a high-intensity training stimulus, a muscle needed roughly 48 to 72 hours to fully repair and supercompensate.
Within the first 24 hours after training, the rate of muscle protein synthesis peaked.
24–48 hours: Synthesis remained elevated. Satellite cells (muscle stem cells) were activated and began to differentiate and fuse with existing muscle fibers, making them thicker and stronger.
After 48–72 hours: Repair was largely complete. If nutrition and rest were adequate, the muscles entered the "supercompensation" phase and became stronger than before.
But Hiroki's script eliminated the initial 48–72-hour repair cycle. It kept the muscles constantly repeating the golden phase of growth and "supercompensation."
Under long-term training, a control experiment would normally take four to eight weeks to observe significant, stable muscle growth.
A large rat weighing 400 grams might gain only a few tenths of a gram of pure muscle tissue (dry weight)—for example, 0.1 to 0.3 grams—during one perfect 48–72-hour "supercompensation" cycle.
That number might seem insignificant, but it was already an efficient adaptive response, refined over the course of evolution.
What's more, various factors could reduce muscle growth along the way, such as inadequate training, inflammation, or excessive injury.
And training itself took time. High-intensity training couldn't be completed in a second. Injury during training was unavoidable, too.
But after using Hiroki's script, everything changed. The script forced the body to remain at the peak of the "golden window" around the clock. There was no need for training, a recovery cycle, or muscle repair.
Only growth mattered. Only peak efficiency!
One week = 7 days × 24 hours/day = 168 hours.
Those 168 hours represented 100% continuous peak synthesis, without any decline.
For reference, consider a large rat: a healthy adult male wild rat with a baseline weight of 400 grams (already a fairly large specimen).
Muscle tissue made up about 45% of its total body weight, or 400g × 0.45 = 180 grams.
Muscle was about 75% water and 22% protein, with the remainder consisting of fat, glycogen, and so on. So, the 180 grams of muscle contained about 180g × 0.22 = 39.6 grams of pure protein.
A normal rat ate an amount of food equivalent to 5–10% of its body weight each day. But in the extreme hypermetabolic state caused by Hiroki's script, its appetite would be enormous.
Let's assume the rat could eat about 15–20% of its body weight in food. Hiroki was providing chicken-based feed, which was high in protein, at around 25%.
Using the lower estimate of 15%, its maximum daily protein intake would be 60g × 0.25 = 15 grams.
Assuming a biological absorption rate of 90%, it would actually absorb as much as 13.5 grams of protein.
Normally, only about 5% of that protein would be used for muscle growth. But...
In Hiroki's control experiment, the white rat, freed from the restrictions on muscle growth, used almost 25% of its protein intake—about 3.3 grams!
Keep in mind, this was pure protein, not muscle yet!
To work out how much muscle that meant, we could use the usual estimate that muscle contained around 22% protein.
Daily muscle synthesis by wet weight = 3 grams of pure protein ÷ 0.22 (protein proportion) ≈ 15.3 grams.
In one week, that amounted to nearly 107 grams of pure muscle!
Of course, as its body grew, its ability to eat and digest food would inevitably become less efficient, and its rate of muscle growth would slow. But for Hiroki, even three kilograms of muscle in a week—not to mention thirty-one—would be something bodybuilders would need an unbelievable amount of hormones to achieve!
But just as Hiroki was stunned and delighted, thinking he'd succeeded, the very next moment—
The little rat running at full speed suddenly twitched twice, then stopped moving.
A faint, pungent smell of urine drifted from the cage.
Before you continue