The lab sounds made for a strangely calming vibe. Which was perfect, because that's exactly where I was.
On the table in front of me lay Might Guy, wrapped up in thin threads of chakra. Another modified version of the Mystical Palm pulsed softly, feeding straight into the patient's chakra pathways. The familiar "easy" damage—torn muscles, broken bones—had been fixed almost instantly, basically back in the forest, on the fly. But that wasn't the end of it.
The Eight Gates—Hachimon—is a forced overclock of the body and the chakra circulation system. A targeted activation of a cascading breakdown. It literally burns cells, dumping all their life energy into one short, destructive burst. Structural degradation of tenketsu, the channels losing integrity on a subatomic level… basically, the body "burns" itself to squeeze out way more than a hundred percent of its original max.
There's a reason this technique is forbidden. Modern medicine says the damage Hachimon does can't be fully repaired, period, and it hits the organism hard. The brawling brute sprawled next to me was lucky—he happened to be on good terms with, probably, the only person alive who could actually fix him completely.
Healing Guy's chakra circulation system wasn't "impossible" for me—just a pain in the ass: you have to do a ton of calculations to generate a system like that for a specific body, then patch it up point by point. All in all, it took about an hour.
When Might woke up, he opened his eyes and for half a minute just stared at the bright ceiling. Earlier I'd moved him into another room of the lab—one without any equipment.
"I've never felt this good…"
"As a med-nin, I've got access to certain… special means," I said with a faint smile, standing about a meter from the bed Guy was sprawled on.
He sat up without any trouble and looked at me, confused. Everything was lined up perfectly for realization to bloom in his eyes, and—
No. He didn't get the joke.
Instead, he immediately launched into a speech about what an amazing spar we'd had. How, for a man living for taijutsu, it was the highest honor to fight a worthy opponent. To go all-out, and all that stuff.
I listened for about four minutes before I managed to shake off this "Noble Beast."
Truth is, the spar really was good. I just didn't enjoy listening to some weird dude shouting his lungs out.
Hirudora—Daytime Tiger. Using my body and chakra circulation system to the fullest, but without opening Hachimon, I managed to replicate it… kinda. My body was just titanically strong and tough. If Guy had been my enemy, and if I hadn't redirected the energy of that strike, I would've gotten away with nothing but a burn. But for Might, even just using the technique was already breaking bones—and if I'd piled on more load by meeting him head-on, he wouldn't have held up.
The idea that I don't use the Eight Gates isn't exactly true. The first gate—the one that lets you use a full hundred percent of your strength—is basically always "open" for me. Or rather, it's not even there, because my body's durability lets me do without it. But I can open the others. Now, after studying Guy up close—someone whose chakra has already opened those Gates—I can say for sure: I know how, and I can do it.
And not just the seventh.
My body is on a completely different level. The regeneration I built into it is so strong that, by my most plausible theories, I could even afford to open the Eighth Gate of Death. Of course, it won't be consequence-free. The technique still implies "burning" the body and the chakra circulation system itself—only even harder than with the Seventh Gate. If I burn through half my reserves in that mode and live, I'll end up weakened by way more than half after the fight. I'd have to spend a long, tedious time patching the scorched circulation system and restoring my body. In the near future, there probably won't be a reason for a suicidal burst like that. But the very fact it's possible is… motivating.
Speaking of possibilities. My sensory perception after the upgrade also hit a new level. Sensitivity to chakra flow, to muscle movement, to the structure of techniques themselves became comparable to the Sharingan—if not straight-up better. That's exactly why I could analyze and copy Daytime Tiger on the fly, just from seeing how Guy formed the pressure and concentrated power.
I was already thinking what to do next. After I finished with Guy, I wanted to rest a bit. Maybe meet Hinata, or check how Sakura's training was going. But those plans weren't happening. I didn't even make it out of the house before an ANBU guy materialized at my door.
"Uzumaki-san. Hokage-sama requests your immediate presence at the residence."
So much for rest. I've got a pretty damn clear guess what the old man wants from me.
Hiruzen looked like someone had beaten him with a sack and then punched him in the gut—completely wrung out.
After greeting him, I sat down across from him.
Without a word, he put an ANBU report in front of me, along with a photo that I assumed was taken with some Telescope-Technique knockoff.
"This… was your doing, Naruto?"
The picture showed a fresh crater. Huge, melted over, like a meteor had slammed into the ground. Around it—a whole kilometer-wide zone of forest burned down to nothing.
"Yeah. Sparring," I answered shortly. "Got a little carried away."
"'A little'?" His voice was pure helplessness. "Naruto, you changed the country's topographic map! Sensors all along the border recorded a chakra burst comparable to a Bijūdama!"
I squinted at the photo harder, picking it up.
"They're full of it. A Bijūdama's weaker."
Hiruzen just stared at me in silence. I could see his world collapsing in his eyes. A world where he was the Hokage—this wise mentor, a guardian. All of it was falling apart, because it no longer fit his picture of reality. Now, in front of him, sat a conduit for power he couldn't understand and couldn't control.
"Oh, quit panicking like that. Everything's fine." Trying to calm the rattled man down, I turned the photo toward him and started tracing it with my finger. "Look, right here in the pit, a lake's gonna form soon. And just look at this weird ground—burned black. Huge area, totally clean, nothing to clear out. You could build a resort here, the kind you won't find anywhere else. The forest over there is already knocked down—construction will be even cheaper. Imagine it: scorching sun, palm trees on freaky black soil, and all of it by a deep lake. I mean—perfect project, right?"
Then I put the photo back on the desk and watched Hiruzen stare at it blankly.
A bit more time passed before the old man let out a loud sigh.
"You know… Naruto. I already regret bringing this up. So I'll only say this: Guy's mission was classified. The only person who knows you did this is me."
"Mhm. Secrecy," I nodded at his measures. No point letting enemies know too much about what we can do. Then a thought flashed: if they didn't let me relax now, maybe they'd let me later. "I worked a lot to get this strength. And I'm tired. Maybe there's some mission for me… something harder?"
Yep. I considered an S-rank mission a form of rest. But I didn't get what I asked for. Still—since I'd brought up dangerous shit, they did tell me something interesting.
The Hokage gave me info on Akatsuki. A currently small group of elite shinobi whose goal is to collect the bijū. It's sold as some utopian endgame where they use the tailed beasts' power to bring peace to the world. But right now the organization isn't having the best time—they need to toughen up and even recruit more members.
Meaning they'll come for me as the Nine-Tails' jinchūriki—just like in the Naruto story I know from meta-knowledge. But everything the old man told me basically meant one thing: I've definitely still got time. Two years, at least. Which means I don't have to start sprinting around cutting everyone down right this second. I can stay in a relatively safe village until they start moving and keep building power. Because once they start, it'll be obvious—since I, as the host of half the Nine-Tails, would be sealed last anyway: the Kyūbi's chakra volume is too huge to seal first.
Even now, I've got decent odds of handling all of Akatsuki alone. With tactics and shinobi squads involved, those odds get stupidly high. But Akatsuki are still pretty damn dangerous enemies—one of them has the Rinnegan, for starters. And if I've got the option to quietly "bulk up" a bit more, I'll take it.
After saying goodbye to the Hokage—who approved my approach of "sit in the village longer"—I finally went to rest.
After inviting Hinata and Sakura to one of the nicer snack places in the Leaf, we had a good evening. They ate themselves full; I ate myself stupid. After that, in good spirits, we split up.
Both girls were pretty shocked by the changes in me, then started worrying I'd done something wrong to myself. Mostly Hinata. But a few minutes of convincing them that I'd checked everything thoroughly before trying it on myself was enough to calm them down. Sakura relaxed faster—she'd seen more of what I can do and is way more inclined to believe me right away.
Then the next day, watching Sakura train, I was thinking.
Basically, it just happened that the girl was completely dependent on me. And that meant I could do a whole lot with her, and there wouldn't be any uproar because of it…
So, waiting until she was worn out and absolutely, definitely couldn't resist, I… offered her a body-enhancement procedure.
She completely gave herself over to me—meaning, to my philosophy and instructions. As weird as that sounds for a thirteen-year-old girl. Over that time she'd earned my trust—way deeper than before.
Sakura accepted my offer with honor. I patted her on the top of the head and reminded her she wasn't from the Land of Iron, so she didn't have to act like a samurai, then went off to do the calculations.
Crunching a template for her body—which is female, meaning it differs from a male body pretty damn strongly—wasn't that hard. In my research I never focused only on myself or only one sex. So a few days later, holding her hands, I helped Sakura climb out of the chamber. And then—after making sure she was fine, and waiting until she learned to walk normally without my help—like the absolute asshole I am, I led her straight to the scale…
The look on Sakura's face when it hit her how much she weighed burned itself into my smug mind forever. The camera I used to capture the moment, though, got snatched away and smashed with indignant outrage. But my memory's still with me.
Sakura's enhancement is different from mine. Different balance of changes, different energy distribution. Because her base body was a bit weaker, her strength wasn't proportional—by weight—to mine… but her brain, on the other hand, got improved especially well.
Considering I used my reserves to first build up the potential of her chakra circulation system and "inflate" her reserve to the size of three jōnin. That ate several of my own chakra stores—which, compared to a normal jōnin's, are holy-fuck huge. In the end, she became multiple times stronger than her old self, while her improved brain made her control jump especially hard.
That kind of reserve let me densify my student's body to the point the scale showed a three-digit number that started with a "2." That didn't mean her strength was only seven times less than mine—no, it's less than that, and there are a lot of factors, the main one being chakra power. But Sakura wasn't worried about those details. She was worried about that number.
Reassurances that she was way lighter than me and basically "lightweight" for real, for some reason didn't help. Riding that wave, Sakura kept bitching at me over my jokes, and I found it kind of cute. Like messing with a fluffed-up cat that wants to scratch you but can't—because "the owner's a nimble bastard" and keeps yanking his hand back in time. Honestly, after a period of low emotions, it was really nice to see "old Sakura" showing again.
Still—good things in moderation. That's probably what she decided too, because after a few minutes she calmed down… and started apologizing for her "unworthy" behavior. Not like she'd just gone a bit too hard with her expression—fully deserved from my point of view, by the way—but like, I don't know, she'd accidentally burned down my house and my lab worth over a hundred million ryō. I accepted the apologies fast and started convincing her she hadn't done anything wrong. After a minute of coaxing she gave in and accepted that everything was fine… out loud. My "eloquent" look made it obvious as hell I didn't believe her, and she just turned away. Anyway, we dropped it.
After adding "cut off the supply of samurai literature into Konoha" to my to-do list—before Sakura picks up even more crap from there—I started planning the next project.
Going by meta-knowledge, what is this world most famous for? Honestly, I don't know—I haven't seen any statistics. But according to the authoritative opinion of one reincarnator, this world's famous above all for special eyes—the Sharingan.
That moment when, right in the middle of a fight, using nothing but sensitivity to energy and all-around vision, I copied Guy's technique was just—holy shit. And I really wanted an even cooler analyzer. And the fact that I already had a ton of bioengineering data on the topic—and, on top of that, I'd even touched those special eyes and had a pretty blurry idea of how to make myself something like that—only fed the itch.
Getting samples for research was easy as hell. The scheme was already tested: offer Sasuke a spar; knock him out; drag him into the lab for a few hours. And for comparison—minus the "offer" step—I also dragged Kakashi into the lab with his Mangekyō.
After I was done with the Uchiha and finished copying all the data off Hatake too, before I really dove into the research, I had a short talk with Kakashi. The reason was the fūin seal I found straight up in his brain, which—yeah, that one surprised the hell out of me—made it possible to remotely subjugate the jōnin.
"Where'd you pick up this kind of crap?" I asked when he woke up.
"No idea," he answered, clearly not in the loop.
I nodded, deleted that filth, and after telling him not to wander around sketchy places—unless he wanted to "catch" something else—I kicked him out of the lab. And only then did I get to the real work.
It took a few days to organize all the data, but in the end I had a pretty broad knowledge base on the Sharingan. Put simply, these eyes turned out to be an insanely complex biomechanism—the result of intertwined genes and fūin commands shaping their structure.
If I dumb it down hard and really try to force the analogy, you can think of dōjutsu as a core and layers. The core is a semi-unique set of chakra properties and genes. The layers are what the core grows over itself, like tree rings. The first completed layer is the three-tomoe Sharingan. The second is Mangekyō. The third—the deepest and most complex—is the Rinnegan. Each next layer is stronger, but each demands way more from its user.
And here's the main thing: the stronger the layer, the "thinner" its properties are—and the worse they get passed down. Kakashi's eye, for example, will never evolve into a Rinnegan—its core simply doesn't have the necessary "blueprints," everything got lost among the bastar—ahem—among time. Sasuke's eyes are different, but not because of his bloodline. Indra's construct is slowly but surely embedding the missing properties into his core, preparing him for future evolution. Even so, that process is unbelievably delicate. I could understand and copy the properties for Mangekyō, but the Rinnegan still stayed beyond my perception.
Moving on to what I actually managed to study—regular Sharingan. Roughly speaking, it has two main functions. The "Eye of Insight"—super-perception that lets you see chakra flows and track movements so fast it feels like you're seeing the future. And the "Eye of Hypnotism"—a powerful genjutsu tool, from simple suggestion all the way to full-on control. Sure, I could plant commands in someone's mind myself, like I did in the Land of Waves, but the Sharingan made that whole process stupidly easy.
On top of that, there were two ultimate built-in techniques—Izanagi and Izanami. Both "burn" the eye, almost like the Eight Gates burn the body. Izanagi briefly turns reality into an illusion, so to speak, letting the user "rewrite" their death or injury—restoring the body to an ideal state using an embedded template, a kind of affinity (similar to my regeneration construct, except it's instant). Izanami creates a self-restoring genjutsu construct that locks the target in an endless time loop. You can only escape it by accepting your fate. And that "fate" is chosen by the user.
Next—Mangekyō. Besides access to Susanoo, the huge chakra warrior, awakening this stage gives the user two unique abilities. And this is where heredity gets really interesting.
You can imagine the core of each dōjutsu as a "tub" full of potential properties. That "tub" gets inherited with different levels of "fill." Then, using that "tub," plus the user's knowledge and even their desires, the core forms unique abilities. Sasuke's "tub" had lots of stuff tied to genjutsu (Tsukuyomi) and black flame (Amaterasu). Kakashi's (or rather, Obito's) "tub" leaned toward space-time techniques (Kamui). Meaning the abilities weren't pulled out of thin air—they formed for pretty understandable reasons.
So yeah: regular Sharingan properties are fairly "thick" and almost always get passed on in full. Mangekyō properties are much thinner, and what you inherit depends on how lucky you got with your ancestors. Rinnegan properties are even thinner—like, insanely thinner—and in the eyes I studied they didn't manifest at all, lost across generations of their predecessors. Only after Indra's construct does evolution into the Rinnegan become possible. Well. Probably.
That thinness is almost inversely proportional to the dōjutsu's power. And to how many properties you need for the evolution in the first place. Maybe whoever designed this shit—if there even was a designer—understood what kind of power they were handing out, and weak inheritance was necessary. The inability to reliably inherit it through inbreeding could also be a safeguard. Both against the dōjutsu, in one possible timeline, ending up on someone else's side. And, probably even more importantly, so weak, diluted descendants don't awaken eyes that can kill them. A vassal is only good if you can get something out of him. Getting something out of a dead husk dried up by an energetically overpowered dōjutsu is a lot harder. All of that's guesswork, but it sounds true enough. Those eyes came from the Ōtsutsuki, and they've got a main and a branch family, supposedly. Members of the younger branch, being weaker, could very well fail to withstand the Rinnegan. Just like normal people wouldn't withstand it either—hell, even very talented jōnin feel like shit from Mangekyō alone.
Though that second point is either less likely, or it's just a second line of defense. Because a host that isn't strong enough, even after Indra's construct does its thing, still won't awaken even a basic Sharingan unless they meet the strength "requirements."
Studying all this gave me ridiculous opportunities. Essentially, I got a manual for using other people's techniques. Amaterasu, Tsukuyomi, Kamui—now that I knew their "code," I could model and reproduce them.
With all that knowledge, my clones and I immediately jumped into experiments.
Awakening each stage of a dōjutsu is based on concentrating a special chakra in the eyes—formed by the brain under the influence of strong emotions. But you also need strong chakra to begin with. Sasuke, even if I carve up his whole family in front of him ten times, still won't awaken Mangekyō right now. Not enough muscle.
But I didn't need emotional spikes. Thanks to what I knew from constructs, medical ninjutsu, the structure of the dōjutsu themselves and the techniques—especially Izanagi, for even cleaner deconstruction—I could directly transform subjects' eyes according to the needed template. And thanks to the raw power of my chakra and no less ridiculous control, I could "force-awaken" the stages I needed in them. It was complicated, sure, and I couldn't do it without crutches like fūin to make the process easier. But it was doable.
Test subjects started flowing in again, in little streams. I needed hundreds of tests, to check every hypothesis. God, it's good I've got clones—everything can be done in parallel.
Days flew forward. If not for trips outside, for time spent with Hinata or Sakura, I probably would've completely lost my mind… though maybe I already did. But as long as my research kept producing results, and the people close to me were okay, it kept me steady.
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