The Awakened Soul (Naruto SI)

[Welydora]

Having received the method to get into the Ryuchi Cave from Orochimaru, by using a reverse summoning technique with some of his chakra, I found myself standing on solid ground, surrounded on all sides by thick fog.

The world of snakes was not exactly a welcoming place. Case in point: the fog itself was saturated with chakra designed to induce genjutsu that would disorient anyone who stumbled in here.

Orochimaru had told me that anyone who ended up here had to pass three trials, plus one more from the local boss, the White Snake Sage. Pass everything, and the great serpent would teach you her snake senjutsu. Fail, and you get eaten. Simple as that.

The first trial was supposed to go like this: I'd wander through the fog, get tired, get hungry, and eventually one of the Sage's attendant snakes would appear before me and offer food. The trick was to resist the temptation. Give in, and that same attendant would lunge at me for a quick meal. After that, assuming you survived, you'd be escorted further in.

That, however, didn't apply to me.

For snakes, strength comes first. But… they weren't exactly in a position to compete with me.

So instead of wandering around, I said screw the whole trial system, flashed a cross seal, and spawned over a thousand Shadow Clones.

We all sat down and went perfectly still.

At the edge of my awareness, I caught a flicker of someone's surprise. The fog was steeped in the Sage's chakra, and she had clearly sensed my technique. She was watching me now. Meanwhile, my clones and I, planted right in the spot where snake natural energy was densest, began absorbing it at full throttle.

Just a few minutes… and the clones, literally dissolving into the air, snapped back into me in a second, flooding me with chakra and knowledge. Then I got to my feet, and beneath my eyes sat purple markings. Snake Sage Mode.

"This energy feels different… Cold. Slippery," the thought drifted through my head. I slid a long tongue out and ran it across my lips. "Yeah, there's something to this…"

At that moment, the fog began to warp, churning and shuddering. Through the chakra, I started feeling someone's emotions of total holy sh— Surprise!

The reaction was even more over the top than Fukasaku's had been when I'd picked up toad natural energy at ridiculous speed.

With a quiet smirk, I tore open a rift in space through sheer will and stepped through into a large, dimly lit chamber.

Before me rose an enormous throne with a single armrest, upon which sat… reclined? Simply a ginormous white snake! Her scales were clearly visible, each one overlapping the next, every single scale roughly my size. Only a couple of coils of her body rested on the throne itself, leaning against that one armrest like a spool, while the bulk of her tail stretched behind it, wrapping around the columns. Her total length was well over a hundred meters. On her head sat a turban with two sharp points, a red sphere on top, and next to it an orange… wig? Snakes don't grow hair, do they? But the most remarkable thing about her right now was her jaw, hanging wide open in pure shock, and a pipe lying at the foot of the throne with a cigarette still smoldering.

"Ahem." I turned away, my face showing nothing.

And the snake, to my satisfaction, recovered quickly. In my spherical vision I caught the tip of her tail shooting out to knock the pipe, then she caught it neatly in her mouth and composed herself.

"Greetings to the Snake Sage," I began diplomatically, keeping my expression even as I turned back to face her. "May I consider the trials passed?"

"Sss-sss!" She took a long, deep drag, then, thoroughly demolishing whatever was left of her grand and imposing image, choked on it. "Kha-kh… Greetings… You may— kha-kha!"

Choking on the smoke a second time, the snake just spat the pipe out entirely. It sailed past me and clattered against the floor somewhere behind my back.

"Excellent," my humble self gave a measured nod. "I want to learn everything you know. Is passing the trials sufficient for that, or do I need to do something else?"

The snake went still. Her eyes glinted with thought and a kind of greed mixed with wariness.

"The trials are designed to prepare one for using senjutsu… Spirit, body. But you… taught yourself. In four minutes. Why would you need more? I doubt I could teach a being that seems born for natural energy…"

Wrestling with her greed, she managed to hold herself back and started trying to talk me out of it.

"It'll be faster this way," I shrugged by way of explanation. "You might have techniques I'd never think of on my own. Of course, I could get them from Orochimaru. He doesn't use senjutsu himself, but he's studied it. Including the senjutsu of the Jugo clan, which originated from here. But I'd rather learn from a more experienced practitioner."

A passing thought crossed my mind to also brag that this body of mine hadn't even been optimized for natural energy absorption yet. But I decided not to pull the conversation off track.

"Orochimaru… He brought renown to the Snake people on Earth," the Sage acknowledged with a nod. "However, my techniques…"

She sank into deep thought.

"…are worth considerably more. Bring me a thousand living sacrifices. Humans. And I will teach you everything you wish to know."

I let out a short laugh and crossed my arms.

"Bold ask. A thousand living humans would come in handy for me too, honestly. Any chance you'd take a different form of payment?"

"Mhm." She shifted on her throne. "Your blood…"

"No. Snake natural energy eases genomic absorption, as far as I know. My genome is worth far more than that. As for the price… isn't strength above all else in your culture?"

The Sage gave a careful nod, and I broke into a warm smile.

"Amaterasu…" The word left my lips as my eyes ignited with the crimson of the Mangekyo, and the world was swallowed by dark flame in two curving rams!

The fire encircled us without touching, filling the chamber with the crackling and hissing of stone floor burning away. But the snake recoiled from it, pressing deep into the throne with jaw agape in horror. Already white, the snake went even whiter and paler. She clearly knew exactly what this technique was.

"Then here's my proposal. You teach me everything you know. And I don't burn you alive. Deal?"


A few days later, patting myself on the back for my diplomatic skills, I had wrung every drop of knowledge from the head snake and, naturally, the rest of her snakes too.

Now, in the main hall of my laboratory, I was laying out massive fuinjutsu arrays across the floor while carrying on a conversation with Orochimaru, who was strapped down in the center of the room. Now my gift from Hiruzen.

"And what were you badmouthing them for? Sweetest creatures ever."

"Just for their help in attacking the Leaf, they demanded over two thousand sacrifices…" the Sannin replied, strapped to a surgical table and rolling his eyes. "They are the most awful summon contract. Other clans rarely ask for payment at all."

"You just don't know how to negotiate."

For a couple of hours we traded barbs while my test subject talked himself hoarse. He understood this was the end, and here's why:

"Well then, ready?" I retrieved Shisui's eye from a seal. "Soon you'll be a new Orochimaru. And after that, I'll put a new, special Cursed Seal on you. Ironic, isn't it?"

"I used to think life was like a millstone… But now I understand: life is a boomerang," he turned his eyes to me. "It's deeply unfortunate that the real me won't be around to watch you end up in my place."

"Yeah," I shrugged with complete sincerity. "Now say goodbye to your naz— Actually, never mind. Just… bye."

With that, I channeled a massive amount of chakra into Shisui's Mangekyo and got to work on Orochimaru's mind. Before long, he was my absolute slave. His entire personality had been rebuilt with me at its center. He'd sooner become a vegetable than dare betray me.

As a second line of defense, I slapped a Juin on him, one far more powerful than anything Orochimaru himself could produce. And more reliable too, built on the principles of the constructs of Hagoromo's children, meaning this Juin wouldn't fade and wouldn't let the snake act outside his parameters even if I died. Well, provided Orochimaru didn't leave Earth for too long after my death, but those were just details.

After that, I ran an enhancement procedure on my pet lab monkey, not only healing him completely but elevating him from a merely very useful subordinate into my right hand. A hand capable of killing even the strongest Kage, if I willed it.

Hiruzen had asked me to take care of his student. But he'd also asked me not to kill him. Well. Wish granted.

In the near future, I'd extract all of the Snake's knowledge: his understanding of senjutsu, Juin, genomes, and biology in general. After that, I'd find a use for him.

But today, the snake was dealt with. Leaving him sitting in the lab, I headed out in the evening to search for another person who'd be useful to me.

Before long, in a small town, my eyes landed on a mid-sized tavern-slash-gambling den. In I went.

A drunk nearly crashed into me in the doorway, but my agility was more than enough, so I easily sidestepped the man and slipped inside.

Turning into the section of the building where small booths were sectioned off by three walls with tables and couches across from them, I stopped in front of the person I was looking for.

Known in certain circles as the Legendary Sucker for her passionate dedication to gambling and her almost supernatural ability to lose at it, winning maybe once a year if she was lucky. Her other defining trait was alcoholism, which she could justify as: "Gotta spend the money fast, 'cause it sure as hell won't be there later."

But in general, her name was Senju Tsunade. A blonde in a gray tunic with a massive neckline for equally massive tits. Right now, in a clearly tipsy state, she was sprawled face-down on the table, one hand still clutching a half-finished bottle of sake.

Across from her sat a girl with straight black hair to her shoulders, in a dark blue kimono with white trim, and right beside her, a smallish pig in a red vest and beads.

"Greetings," I said, as all three turned their heads toward me. "Tsunade-san, I have a small request."

My calm tone made Shizune, the girl in the kimono, flinch, her eyes going wide. Tsunade, for her part, had barely lifted her head off the table, and her face scrunched up in baffled irritation.

"The hell you want, kid?"

My face twitched at that… Still, I showed no other reaction. The people of this world were rarely acquainted with high culture.

"Lady Tsunade, this is that Uzumaki Naruto, the one who—" Shizune launched into a rapid-fire explanation, getting nothing in return from her sensei but "yeah right," "quit pulling my leg," and "oh wait, I think I heard something about that…"

A minute later they were done, and while I graced them with my slightly irritated look, they were scanning me with something between suspicious and surprised. The pig just looked curious.

"Alright, say all those rumors are true. I'll repeat the question syllable by syllable: what. did. you. come. here. for?" she asked, now sitting upright.

"The slug summoning scroll," I answered, and without waiting for an invitation, sat myself down on the couch next to Shizune.

Confusion crossed Tsunade's face. Not at the gesture, but at the request.

"Word is you're the Toad Sannin. What do you need it for? A shinobi can't master two types of natural energy."

"Your information is wrong," I answered simply, then absorbed a small amount of natural energy in a second.

Markings immediately bloomed across my face, spreading out from around my eyes, mostly along the sides, all the way to my ears, with slightly less going downward. On my forehead appeared a ring with a dot in its center, a mark somewhat resembling the urna, the Buddhist symbol of enlightenment, the third eye. All of this was in a very, extremely recognizable style for Tsunade.

After that, I felt not only the usual boost from natural energy, but also enhanced regeneration, Mokuton amplification, and… a boost to light techniques.

Tsunade's mouth fell open. Shizune's too. Not as wide as the head snake's, of course. But still pretty good.

A thoroughly satisfied grin spread across my mug.

"Should've learned senjutsu sooner. This art has one hell of a reputation," I noted internally, then addressed the woman across from me. "Your grandfather entrusted his legacy to me. The world is changing. I'm the one changing it. And for that, I need even more power."

"This can't be…" She stared at me in disbelief, hands already moving through seals. "Kai!.. This can't be…"

"Nothing is impossible. Will you help me?" I asked, then without ceremony reached across the table, grabbed some of the sliced chicken breast sitting there, dipped it in sauce, and started chewing.

Staring blankly at me, Tsunade couldn't get a word out.

"No… you don't get it, this changes nothing!" she snapped to her senses, voice rising sharply. "My grandfather… he was incredibly powerful, but all he did was lay down his life for his dream! You'll just repeat his fate!"

I raised an eyebrow and swallowed my food.

"You're worried about me?"

"Hmph!" She sharply dropped her intensity, sweeping me with a displeased look. "I couldn't care less about you. But I know perfectly well that thousands of people put their faith in people like you. They believe, they share the dream… All so that people like you can die and leave behind nothing but pain! Get out. I have no interest in talking to a dead man walking."

Silence hung between us.

"So she's got some kind of old trauma?" the thought ran through my mind, as I had zero intention of moving from where I sat. I still hadn't gotten what I came for. "You know, a long time ago, when I could still walk under this table on foot," I slapped the table, "I read and heard a lot about you. The greatest medic. Even with all my talents, you were the one they held up as an example for me. But your grandfather entrusted the future of this world to me. Not you."

Her face stayed displeased through my whole speech. But when the last sentence hit, her eyes started darting between me and the bottle. Her face screamed that she couldn't decide whether to shove the bottle down my throat or smash it over my skull.

"He'd probably be disappointed in you if he knew what you've sunk to. A gambling drunk burning through her life for nothing…"

The last word was barely out before Shizune next to me flinched. She was torn between three impulses: smack me for talking to Tsunade like that, try to shield her from me, or grab the pig and bolt before her lady destroyed everything around them.

The Sannin's jaw locked up. But she managed to keep her composure.

"A brat like you doesn't get to lecture me about life," she bit out, folding her arms under her chest, as if deliberately putting them somewhere far from my neck.

I raised an eyebrow.

"I do. The scroll."

A vein popped on her forehead.

"You are absolutely infuriating… Let's take this outside, huh?"

"Fine by me," I shrugged, unsurprised. After all, my words had been a deliberate provocation to get her out of here and change her mind.

Shortly after, so as not to wreck someone else's property, we moved to a wide, empty alley.

Soon enough, standing like a pair of cowboys, Tsunade and I faced each other while Shizune stood off to the side between us, pig in arms.

"Calling me a brat, you were addressing me like a child. Isn't it beneath you to pick a fight with that same child?" I asked, deadpan.

"Lady Tsunade… maybe we don't have to do this? How about you just calmly talk it through one more time?" Shizune was the voice of reason.

"I'm just going to teach him a lesson," Tsunade said, ignoring me and addressing her student instead.

"Says the one who isn't in Sage Mode right now," I smirked.

"You can't trust rumors until you verify them yourself. Even if some of them are true, I doubt most of the credit goes to you and not your tailed beast," she said with an air of supreme condescension. "And the markings on your face are probably just skillful props."

"You want irrefutable proof? Fine. Go ahead. You start."

"No. You start. I'll be nice. Young blood. I'll give you a head start."

"Don't need one. And you're not exactly young yourself. Fine, I'll be gracious about it."

"…"

"…"

About five seconds passed. Neither of us moved.

Shizune's looks cycled from wary to just plain confused.

"Ah, screw it!" Tsunade broke first and, planting her feet wide, strode toward me to wind up a punch…

BOOM!

After the deliberately slow strike, one that even a not-too-nimble genin could've dodged, the ground literally exploded beneath us, cracks spiderwebbing in every direction.

In my hand, to her look of surprise, was Tsunade's fist.

"Not bad. For a gambling drunk." My head turned to Shizune. "Don't worry. I'll have her back soon."

And before either of them could do anything, I took the Slug Princess through a teleport, landing in a small clearing deep in a forest, far from any settlement.

Only for a monstrous pressure to erupt from me right then and there! A shockwave blasted outward, ripping trees from their roots within a ten-meter radius. Tsunade wasn't blown away only because I was holding her with my chakra, and she kept her footing.

But it only got worse when two more sources of natural energy surged into me, piling their weight onto the world around us.

The earth beneath us cracked and visibly sagged, dropping us half a meter. My free hand grabbed Tsunade's shoulder and pushed her to her knees, her eyes going wide. The Sannin looked like she'd lost her connection to reality, that was how hard what she was feeling hit her.

"Your grandfather did what generations of shinobi before him couldn't," I spoke, and my voice cut through the rising storm, still reaching her clearly. "Hashirama did what generations before him couldn't. I will finish what he started, in a way he no longer can. I will become the new God of Shinobi. You are already living in my era."

"Wh-what do you want?" Tsunade finally came to her senses and, with effort, raised her head to meet my eyes.

In that moment, my face bore no Sage markings. Just a few black lines around the eyes, showing that even for me, holding three conflicting natural energies in balance with my own chakra was tough. But that only made the picture more terrifying.

"From you? Just the favor I mentioned. And proper respect. If you'd tried to kill me, you'd have shared Orochimaru's fate…" My cold eyes met hers. But warmth and life quickly started returning to them, and in the same instant my mouth curved into a smirk. My palm rested against her cheek. "But you can also come back. I think Hiruzen would be glad to see you. And that shaggy pervert is hanging around Konoha right now."

With those last words, the pressure began to slowly ease.

"I think you'll find your inner world full of color again when you return. And for me, as the future ruler of the whole world, it'll be a pleasure to see you among those who push us all toward something better."

My face settled back into its usual irresistibly handsome default. Tsunade, with the pressure gone, stood and stepped back a few paces. Hugging her own shoulders, she alternated between throwing hard-to-read glances my way and staring at the ground.

"I'm not rushing you to a conclusion," I told her. Then my hands came together in a seal, the ground trembled underfoot, and in the distance trees began rising straight from the soil before our eyes.

Before long, we were surrounded by roughly the same forest we'd arrived in. Even the ground was restored to how it had been.

"I… don't even know what to say," Tsunade said, watching in fascination. "After so many of my close ones dying, I convinced myself all shinobi share one path… into the grave. There are things that follow the rules of this world. That's impossible to change. But then, could someone like you even exist? An anomaly of this world… Like the word 'impossible' come to life."

"What you need to say is that you'll give me the scroll. And that you'll return to Konoha. Get back to work in your field. And of course quit drinking, quit gambling, and start promoting a healthy lifestyle."

"Oh come on…" She tried to sound indignant, but it didn't quite come off. "Anyway… I'll think about it. The scroll I'll give you tomorrow."

"Excellent."

We agreed to meet at the same tavern where we'd first met and set a time. Then I teleported Tsunade back to a surely-already-anxious Shizune. I had warned the latter that I'd return her dear lady, but that probably hadn't calmed her entirely.

The next morning, right on time, I watched a trio approaching the agreed building: two women and a pig.

Tsunade, face revealing nothing, a big scroll tucked under her arm, walked up looking like a dad carrying a roll of toilet paper.

"Here," I got what I wanted. "Return it to Katsuyu later. She'll sort it out."

The old dismissiveness was gone from her voice, which I found satisfactory. It wasn't exactly deep bows and ballads praising the great me, but it'd do.

"Have you thought it over?" I asked about her returning to Konoha.

"I'm… still thinking…"

"Good. Just don't go on a bender," I advised, watching with a smile as her cheek twitched.

"I don't even drink that much…" she tried to defend herself.

I didn't actually know enough to say that for sure. But someone nearby promptly confirmed it.

"Lady Tsunade…" Shizune said, in a tone that made everything perfectly clear.

"Hey! Whose side are you on?!"

"I could set up an aversion treatment," I said to the dark-haired girl, covering my face from Tsunade's side with my hand, as if she couldn't hear. "I have some… knowledge of medicine. I could modify the taste perception on her tongue so alcohol would taste like piss."

"That won't be necessary!" Tsunade blurted, stumbling over her words and not daring to raise her voice too much at me. "I'll seriously think about it."

On that note, our meeting was over. Saying my goodbyes without much delay, I teleported home and quickly studied the scroll. Having gotten the path I needed, I set out for a place I'd never been to before.

The Forest of Damp Bones. The Shikkotsu Forest.

---

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[Welydora]

The moment I shifted into Shikkotsu Forest, I felt damp soil beneath my feet as a faint acidic scent hit my nose. Looking around, I was greeted by arches and curved obelisks filling the space, bone-like structures overgrown with fluorescent moss. All of it in a dim setting, as though it were evening outside.

Unusual, I noted. Though I suppose that's how it should be in another world?

The Forest of Damp Bones. A very fitting name.

Originally, I'd come here to study senchakra, but I decided to explore my surroundings first. Approaching one of the bone-trees, I ran my hand over the cool, damp moss.

So it's not actually bone after all, the thought crossed my mind. Just calcium deposits from slug secretions. How many years have they lived here to build all this?

Hopping onto a large bone, I surveyed the forest stretching for kilometers beyond the horizon.

My exploration didn't last long, though. My hearing picked up movement just over a kilometer away…

A blink, and I found myself before a fairly large slug, roughly my size, resting on a rib that hung suspended above the ground. And it… differed from the Katsuyu I remembered: the body of the slug before me was simply translucent.

"Hello," I greeted in a friendly tone, and a pair of eyestalks slowly turned toward me without so much as a flinch, the creature's eyes resting at their tips.

"Greetings, Uzumaki-san…" came a very soft, and what seemed to me, shy female voice. "Katsuyu was expecting you closer. We are far from the Heart."

"Oh, so Tsunade actually bothered to give a heads-up about me, rather than just handing over the scroll. Nice."

"I know little. Tsunade-san spoke with the main consciousness. But for those like us, it's difficult to receive much information… It's troublesome."

"Those like you?" I clarified.

"I don't think it would be useful for you to hear about the life of simple slugs," the little slug deflected with apparent embarrassment, steering away from the topic. "You need to go that way." She turned, indicating a direction with one eyestalk. "You won't miss the right place; it… stands out. But if you stray from the path, just wait. Those like me will find you and show the way. Also… don't approach the transparent lakes. The acid there is incredibly strong. Even the fumes will kill you… Good luck on your journey…"

Modestly finishing her instructions, she continued watching me with the same expression.

I told her something along the lines of, okay, I won't force you to talk if you don't want to, and hopped off in the indicated direction. Just like a regular shinobi, only way stronger, so my leaps carried me hundreds of meters at a time. Along the way, I did encounter the mentioned lakes, which I gave a wide berth.

After covering twenty kilometers, I was met with the sight of a massive, simply colossal ribcage belonging to some unknown creature, over seven hundred meters in height alone. In the mild gloom, the glowing moss that covered these "bones," just as it covered everything else around, looked especially enchanting.

Soon, I approached the entrance of this enormous structure, right up to large, wide-open gates that appeared to be made of bone. Around it were huge thoroughfares crafted from the same material, and in the distance, many smaller buildings. There were also a lot of slugs moving in every direction, though most of them looked the way I remembered: white with three blue stripes running the length of their bodies.

One of the latter, about four times my height, smoothly slid up to me.

"Uzumaki-san," I heard a voice slightly different from the other slug's. Still soft, but less timid, maybe? "I've been waiting for you. Call me Katsuyu."

"A pleasure to meet you. Life's really bustling around here, huh?" I said, smoothly taking another look around.

"Shikkotsu Forest requires constant supervision… so that anomalies don't occur. We take care to ensure this world is safe for both us and our guests. But let's move to the main body."

I agreed, and we headed inside. This "Heart" wasn't the kind of structure familiar to humans, not like the toads' buildings. It was far more natural and unified with nature, its interior completely filled with greenery.

After walking about half a kilometer, we entered a massive hall. On a small green pedestal sat a low, black basin, and inside it was a slug body with the exact same coloring as my guide… Only the size! She was enormous!

I'd previously thought the toad bosses were big, but this Katsuyu's body was about four times larger! Her head towered hundreds of meters high, making me look really, really small next to her.

The basin itself was much larger, and the ceiling even higher, so this slug could comfortably fit here even if she were several times bigger.

Walking up, I craned my neck back and waved to her in greeting.

"So, I came to learn the Slug Sage Mode. Will you teach me?"

"Tsunade-san said you would come with this request, Uzumaki-san…" the same voice came from the larger version of Katsuyu. Now, however, worry had crept into her timbre. "But I see you've already mastered three types of senchakra… Each natural energy seeks to transform the vessel in its own image. A-are you sure you can resist?"

"Quite."

Instead of verbal proof, I gave a visual demonstration. Black lines, like cracks, instantly surfaced across my face as three types of senchakra invaded my body simultaneously.

"This is remarkable…" my conversant above seemed to whisper. "Usually, you humans evoke feelings of interest and affection in me… So warlike, yet so fragile. Only a handful among you are even capable of touching natural energy. Only to die a terrible death…"

"You could say I've spurned weakness," I replied, spreading my hands, then exited Sage Mode. "I'm all ears, Katsuyu-san."

"Very well. I will fulfill Tsunade-san's wishes," she said, and began her explanation.

Since ancient times, Shikkotsu Forest had been the summoning contract of the Senju clan. Having gone through so much with that family, Katsuyu held deep loyalty to the last Senju, Tsunade.

Slug senjutsu didn't have a specific human-oriented style. The shinobi who could have developed one were simply too few, and even those struggled terribly with the natural energy itself, spending all their focus just trying not to die. Inventing a style and techniques was a long way off for them. The slugs themselves weren't a warlike race, but rather a utilitarian one. Or rather, Katsuyu herself was…

The primary ability of slug senjutsu, which unfortunately only worked fully on the slugs themselves, was division. In fact, almost all the slugs were one being: Katsuyu! She had simply divided herself. But she could gather back together, reaching a size roughly ten times that of a toad boss.

When divided, each part of Katsuyu maintained an incredibly strong and broad connection with her. This was another ability of slug senjutsu. Through this connection, they could transmit chakra and communicate directly, and all of it worked across any distance on an Earth-like planet, as well as between dimensions.

Naturally, there was also the fact that slugs, and by extension their senchakra, had a massive predisposition for regeneration. In seconds, Katsuyu could split into thousands of slugs, then reassemble just as quickly.

As for combat, the slugs basically only had acid. Very corrosive, by the way, and they could shoot it in a wide or concentrated stream. But that was it.

Having told me about the peculiarities of her senchakra, Katsuyu suggested I head to the Silent Cavities. That was what they called the caves in this world where senchakra condensed. In some of them, though, alongside the senchakra, there were densely placed acid lakes. Humans were better off not wandering this world on their own; it was dangerous. But they'd take me to a safe spot.

However, I decided to propose a simpler route: have Katsuyu separate a small slug from herself and personally transmit a bit of senchakra through it to me.

That's what we tried, and with her full assistance, it took me only about ten seconds, even without clones, to grasp how to absorb yet another type of senchakra.

A new sensation again, a kind of slickness this time, as if my body had been slathered in top-grade lubricant. Felt like if I wanted, I could squeeze through the narrowest of openings.

"Now let's try all of them…" I wanted to absorb every type of senchakra, and soon enough I… succeeded, with mixed results. "Whoa. Now I look like some kind of poisonous dart frog…"

I commented on the pigmentation that had bloomed across my face from all four natural energies, covering it entirely in markings. Not by my choice. Four types of senchakra were simply too much even for me right now, and my body had taken on somewhat bestial traits.

My skin became genuinely slimy, and I could feel my canines growing in, along with an acidic tang in my mouth.

"Ptui." I spat out the accumulated saliva, and where it hit, a small patch of grass inside the Heart began hissing, as though melting everything beneath it. But it stopped soon after.

"Are you alright, Uzumaki-san?" Katsuyu asked with concern.

"More or less…"

Those weren't the only changes. My fingernails had grown out, sharpening to points, and my body had become just slightly, toad-like in its mass. The last one was only visible from the slight thickening of my limbs.

Not exactly some eldritch abomination; my human features still substantially predominated. But the absorbed power thrummed through my entire being. Like shouldering a heavy mace. But if you got a good swing going, the impact would be devastating.

Studying the changes in myself, I extended my hand out in front of me… And then my palm, along with part of my wrist, simply dropped onto the grass.

Seeing this, Katsuyu rippled with alarm.

"Everything's fine," I preempted her reaction. "Turns out the slugs' division ability works better than expected."

Meanwhile, my hand in the grass pushed itself up on its fingers, as if it were still part of me. Wiggling them, it attempted some clumsy little dance, then quickly scrambled up my pant leg and reattached to its original spot with a hiss.

"See?" I showed the slug that my hand was perfectly fine.

"This… is more than previous human sages could demonstrate."

"Thanks for the praise. And… hmm. I feel like with practice, I'll be able to adapt and hold all four types of senchakra just fine. I think my limit is six. Do you happen to know of any other sage animals besides toads and snakes?"

Katsuyu silently lowered her eye-antennae. That alone was more than enough to convey her emotions. "…No."

"A pity. Then, will you tell me more about this place?"

She agreed, glad for the chance to move away from what she'd just witnessed.

Katsuyu didn't know if there were other slugs out there besides her. Sentient ones, that is. She had been born over a thousand years ago as the renewed consciousness of an older slug just like herself. When Katsuyu eventually aged, which wouldn't be anytime soon since her lifespan spanned several millennia, she would sort of cocoon, and from the old slug's body a new one would emerge, with a different personality.

Theoretically, every part currently connected to Katsuyu could be reborn as a different slug.

Long ago, when she first reincarnated… this world had been different. Much more aggressive, completely flooded with acid, with only remnants of life remaining. Katsuyu suspected that perhaps there had been many slugs before her, but her predecessor had simply devoured them all. And then, having lived in an empty world for some time, decided to pass on herself.

Because of that, Katsuyu found motivation to live differently. The world she was born into was unpleasant to her, and the world itself was hostile right back. So, to avoid ending her existence just as meaninglessly, Katsuyu became the architect of this world.

Year after year, being colossally huge from birth and capable of using the local senchakra, she used her smaller clones to physically move the acid, pooling it into large lakes, thereby freeing up most of the space for vegetation. She also meditated, filtering the senchakra of the entire world, which had been too aggressive for the world to recover quickly on its own.

And so, year after year, this world transformed.

Later, after a couple of millennia, several humans managed to get here. A few sentient beings, deciding to bind themselves with chakra for safety, rushed into a reverse summoning and ended up in this world.

Katsuyu was curious about other creatures. Until then, she had seen nothing but plants in this world, no one sentient.

Sending out a small clone, she discovered that the newcomers were quite friendly, and their temperaments meshed well with hers.

Allocating a space for the new residents, the slug coexisted with them for hundreds of years. And over time, she noted, those who could come to this world became increasingly warlike… Not toward Katsuyu, just in general.

Not too long ago, about a hundred and some years back, the Senju begged the slug to occasionally help them in battles in their world. And Katsuyu, having grown quite attached to them by then, almost like pets… didn't refuse.

However, not much came of it. Katsuyu's clones couldn't significantly help in battle, and very few could summon her massive form. And even sheer size wasn't that useful; more the opposite, actually.

Generally, Katsuyu was always summoned in parts. Tsunade, for instance, could summon a tenth of her, which was about the size of a toad boss. But summoning all of Katsuyu was inadvisable: it wouldn't significantly boost her combat power, while her mobility would drop substantially. Plus, as long as the main part of the slug remained in her world, she was immortal and could regenerate. The optimal size, right around a toad boss, let her produce enough acid for damage while maintaining mobility and immortality. Though with her regeneration and ability to divide, killing Katsuyu was extremely difficult regardless.

But the Senju wanted to make the slug stronger. That was how the different slug variants came to be. Previously, Katsuyu hadn't created new varieties of herself since she saw no particular need. Later, humans filled her desire for communication. But eventually, the slug allowed them to experiment on her small parts.

The Senju tried grafting parts of other animals onto the slugs, artificially inducing mutations through chakra exposure, and doing other selective breeding. But they achieved very little.

Most of the variants simply died, which made Katsuyu sad. Those that survived were often very weak and either soon met the same fate, or simply lived out incomplete existences.

In the end, after years, only a handful of more or less successful variants remained today. But even those were fundamentally flawed, incapable of surviving outside Shikkotsu Forest.

There was the Sayu variant, the translucent sensor slugs, like the first one I'd met in this world. Although their sensory abilities weren't all that impressive. Besides them, there were many with various bone-like growths; some of them literally looked like mobile basins, and those were handy for transporting acid. Others had additional front limbs with hard claws, similar to a lizard's. And this whole menagerie could fluctuate in size fairly well.

As it turned out, the modified slugs could only survive in this world if they retained at least some sufficient connection to Katsuyu. They were dependent on her; without her chakra, they'd die. And they were also quite similar to her in temperament.

These slugs connected to her, but not her clones, Katsuyu could reproduce, gradually increase or decrease in size, and give commands to. In practice, Katsuyu held absolute power here, because even if someone rebelled, nothing would come of it. And "rebellions" almost never happened here, considering that all the slugs shared their leader's calm temperament, and on top of that were completely dependent on her.

Ultimately, a full-fledged settlement had formed here. Somewhat similar to an ant colony, but even more devoted to its purpose.

When Katsuyu finished her story and received my thanks, she gave me a clone to show me the way to one more place.

This was the Hall of Contracts, or as the slugs more practically called it, the Bone Rotunda. A large, dome-shaped building of interwoven bones. Stepping inside and seeing the interior, I was surprised to note it was far more human-like. The floor was level, still bone, but without vegetation. Inside were various rooms, the most notable being the Senju library, where they'd mostly left records on slug breeding, and the summoning hall that shared the building's name. The latter was a round room in the center of the building, with a seal on the floor and a small raised platform in the middle. This mechanism facilitated summoning in both directions, and logically, if I had signed the contract with the slugs and properly used the summoning technique, I would've appeared right here. But my great intellect preferred to simply figure out where this world was from the scroll and tear a portal open at random.

With that, my journey to the slug world was over. I returned home and spent a couple of days mulling over the data I'd gathered, while also constantly bugging Orochimaru to share his.

And when I got a little tired of that, just a tiny bit, I switched gears.

Namely, I relaunched cycles of trials on test subjects, this time to address the problem of soul mortality.

Katsuyu had an immortal body; I'd studied that at some point out of curiosity. But her soul still aged over time; I'd tracked that through her emanations as well. Sure, thousands of years was way better than a human's hundred, but I wanted much greater limits for my loved ones.

Except it didn't work right away. The hole problem remained. To strengthen the soul's core, I needed to reach it, boring holes with my energy. But life with those holes was impossible.

I needed to find a way to either force the soul to regenerate… or shove the necessary energy in without damaging it. And the first, as it turned out, I could pull off.

There's a rule in this world: don't know how to do something, throw more juice at it. With care, of course, and accounting for a whole bunch of other factors. But in general terms, that's it. So, by pumping a literal kiloton of my soul energy into one test subject on my lab's surgical table, pouring in nearly all my knowledge of healing, I managed to get some kind of result after about a week. But, unfortunately, it was highly questionable.

Fortunately, the parallel development of the second stage of body enhancement was going better. Though even there, the result was only just starting to come together into a complete picture.

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