Naruto isn't late to class for once in his life.

Sasuke would find it strange, if he cared about that sort of thing.

He doesn't notice something is truly different until first break, when after several unusually quiet lessons, Kiba leaps over the benches to sit on the desk in front of Naruto.

"Hey dude, what the heck happened to your jumpsuit?" Kiba asks.

Sasuke does turn around at that, subtly as not to be noticed. It actually takes him a second to find Naruto, because without the bright flash of color that he wears like a banner, he looks very different. Instead of that horrendous orange thing he usually wears around, Naruto's in a set of standard issue shinobi wear, black sweats and a matching high necked long sleeve shirt. The getup is about two sizes too big on him, but before Sasuke can conjure up something to say about that, he notices that the excess fabric had been tied back with black wrapping above his elbows and at his wrists.

...Surprising practical.

Naruto makes a face at the Dog-nin that's halfway between upset and aggrieved. "It got gross and too torn up to fix, so I had to throw it out."

Kiba pulls a sympathetic expression. "That sucks, I've never seen you without the thing. Had to have been your favorite to keep it around as long as you did. I'm not surprised it crapped out on you though."

Naruto grins up at him, a little bit wry, pulling a hand through his blond hair. It looks brighter against the black than it should be. "Yeah, no kidding. I held onto it because Iruka-sensei helped me make it. Losing it kinda blows."

"That stuff's got to be easier to move in, though." Shikamaru drawls from behind him, head pillowed boredly on his arm. Sasuke would have assumed he was asleep if his eyes weren't open.

"Much." Is the Dead-Last's reply, shifting his arm as if to demonstrate. "Just wish I didn't have to get new stuff, ya know?"

Shikamaru nods, barely perceivable with most of his face hidden in the crook of his elbow. "I feel you man. I hate shopping. What a pain."

Made it with Iruka-sensei? That's why he wore that stupid thing around all the time? Sasuke wonders.

But Sasuke jerks his attention back to the front of the room when Sakura or Ino or someone calls his name, and goes back to pretending like Naruto doesn't exist.

It doesn't work like it normally does though, and even though he keeps his eyes on Iruka-sensei for the remainder of class, he feels some sort of strange gravity churning at his back.

Curiosity and… something else.

The strange sensation that something has shifted, and he can't tell what.

Naruto is so excited about training after he gets out of class, that he nearly forgets about something almost as important.

Food.

~Lunch, brat. You need to eat before we start this.~

Naruto stops with a hand already halfway to his bags of supplies by the kitchen table and groans.

"I totally spaced."

~I noticed.~ Kurama drawls sarcastically. ~I'm teaching you about chakra, so you're going to need your strength. We can go over your supplies while we eat.~

Naruto burns his rice on the first attempt and accidentally makes pudding with it on the second, but the third try is palatable and he does okay with the miso soup and salmon, which is only a little charred. He sets everything down on the table and pulls his equipment out of his bags with one hand while he eats rice with the other.

A brand new set of twelve Jounin-grade Kunai, three packs of assorted shuriken, two bundles of senbon, a fuma shuriken, a steel tanto, twelve regular seal-grade scrolls, two large storage scrolls, fifty paper tags; fifteen exploding, ten flash-bang, ten smoke bomb, and twenty-five blank; and twenty paper seals, half blank and half barrier.

"What am I gonna need anyway?"

~Just the barrier seals for now. And chew your food kit, you're going to choke.~

Naruto has to make a concentrated effort to eat slower– he feels a little like he swallowed a lightning bolt. He taps the barrier seals with one finger as he swallows a bite of salmon.

"So these are what seals look like?"

~Extraordinarily basic ones, yes.~

"How do they work?"

~Patience brat. You can't do anything with those until you learn to mould chakra properly.~

Naruto tries not to pout.

"Oh fine."

~A lesson for another time. We'll get to it.~

"Soon?"

~Soon.~

Naruto finishes his food and tucks the seals into the wrappings on his thigh.

"Where are we going?"

He gets an impression instead of an answer, a set of images and sensations and sounds. The sun filtering through willow branches, the sound of water crashing against rocks, a memory of solace in pain.

"Gotcha."

He clears his dishes and heads east from his apartment, aiming for the outskirts of the village proper. He crosses a river on the outer edge of training ground nine, following it as it curves further from the village until the sound of rushing water gets louder. Here the trees get close and the branches weave together, making the path more and more difficult for him to find his way around. He remembers having ran this way at full tilt, remembers how the branches had caught at his clothes and hair and skin as he bolted through them. This time's he's careful to avoid them as he comes close to the rapids.

He abandons the forest for the sharp juts of rock protruding from the river. It's slow going, since he has to be careful about not losing his grip and falling in. After a bit the area opens up and Naruto can spot the waterfall on the other end of the clearing.

The glade looks different in the afternoon than it had at dusk– the willow is more green now than gold, and the water in the basin shines like a mirror under the sunlight.

~Alright, fishcake. Stick the barrier seals around the perimeter. As evenly spaced as you can.~

Naruto hums his ascent and goes about his task. It takes a couple tries, but Kurama is patient, and by the fourth attempt he's satisfied that the seals are in good places.

"There."

~Good. They're not true shielding seals, but they should keep anyone from noticing any chakra you end up throwing around. Have a seat.~

Naruto plops down among the roots of the willow, jittery and excited. He's never been so hyper to learn something in his whole life.

He feels Kurama's chakra, old and feral and familiar, scorch up through his system. A shade materializes in the air, the same size as the first one. It seems to be about all the chakra Kurama can currently squeeze through the seal. The fox settles so he's eye level, vulpine paws crossed, his tails swishing lazily back and forth.

"Can you teach me how to use chakra now?" Naruto whines. "Please?"

~That was the plan, kit.~ Kurama reminds him patiently. ~So, what do you know about chakra already?~

Naruto racks his brain. He doesn't come up completely empty, when he thinks about it. "There are five types? And what kind of affinity you are determines what kind you can use best."

Kurama huffs and shakes his head. ~This is worse than I thought. Wrong. No offense to your Iruka-sensei, he's close, but most humans have the wrong idea.~

"About the chakra types?"

~About 'affinities'.~

"You mean people don't have affinities?"

~I mean that just because someone has a place they are more comfortable drawing their chakra from, does not mean that they possess only one kind of chakra.~

Naruto shakes his head, forehead scrunching. "I don't get it."

~Let me start from the beginning then.~

The fox reaches up, gently pinching off the end of a willow branch.

~Chakra, in it's most basic form, is the energy generated by existence. It's in everything–grass, stones, the air you breathe and the water you drink. Most things do not produce enough chakra to even sense, but powerful living beings, like shinobi or sage animals, are capable of creating it in an amount great enough to mould.~

A soft pulse of energy and the branch dissolves into white light. Kurama flicks it into the air, and it settles obediently between them.

~For the most part there are seven types of chakra. Nature is balanced by the first five forms; Earth, Water, Fire, Wind, and Lightning.~ As he speaks, Kurama drags from the chakra flare five different spheres of energy as big as fists. The first is greenish grey like old stone, the second cobalt and clear as crystal, the third is bright with flickering shades of red, the fourth is twisted and fast moving but otherwise colourless, and the last is a crackling ball of onyx and silver flashes. They orbit the space left by the central flare in a lazy spiral. ~Each of these forms can be drawn from the parts of the body in which they rest.~

"Rest?"

Kurama nods. ~Each of the elements that balance nature also balance living beings. They saturate and hold dominion over certain systems. The chakra in these systems remains dormant, for the most part, until someone attempts to draw on chakra for the first time.~

"Okay, hold up." Naruto holds up his hands for a time out. Kurama pauses, obviously amused. "So you're telling me that everybody has all five of these kinds of chakra, in the same amount, but people only use one kind? Why?"

~Most human shinobi are born with one of these pathways already open, or find one kind of pathway easier to open up than all the others. This is where I can only assume the idea of affinities originally came from. In truth, using only one kind of chakra throughout your life can cause the other pathways to atrophy.~

"Atrophy?"

~Disintegrate, become useless. The same thing can happen to unused muscles. They just… stop working.~

"That sounds really bad."

Kurama nods gravely. ~That's why I'm going to teach you how to open all five pathways before we even start you on moulding chakra. Keep in mind.~ Kurama holds up a claw to snag Naruto's attention. ~Training all five of these chakra sources means that it will take five times longer for you to learn, not to mention all the other training I'm putting you through. Are you okay with that?~

"Will it make me stronger?" Naruto questions, because that's really the important part.

~It will exhaust you. You'll be tired and run down six days out of seven, and you'll constantly feel like there aren't enough hours in those days. For a while, training will be your whole life.~

Kurama pauses. Naruto remains silent, waits him out, because he can feel the 'but' coming.

The bijuu grins, all fangs. ~But it will make you stronger in ways you've never dreamed of. You prepared for that, Fishcake?~

Naruto sends a toothy grin of his own right back. "Believe it."

Kurama chuckles. ~That's what I thought.~ he sticks the first orb on his index claw, the one that looks like a mossy mountain rock.

~Now, you know that technique you use to talk to me through the seal?~

Naruto nods.

~Do that now, but instead of reaching into the seal, reach into yourself instead. I'm going to give you a taste of the kind of chakra you're looking for and where it comes from, and you need to find it in yourself and try to draw it forward, wake it up. Think you can do that?~

That sounds complicated, but Naruto is nothing if not persistent. "I can try."

~Let me know when you're ready.~

He shifts his shoulders to ease out the tenseness, slows his breathing and closes his eyes. When he can hear his heartbeat clear in his ears, he nods.

There's a sound like rolling gravel as he senses something move to hover over his chest. The energy pulses just shy of his skin, and he can feel the not-quite solid touch of Kurama's claw against his sternum. Kurama's voice echoes strangely.

~Earth chakra is the seat of strength, and is defined by its endurance and stability.~ the ball of chakra tingles as it's pushed into his chest. ~It rests in the bones.~

The power suffuses through him, just a touch of foreign energy that rolls slowly out across his ribs. The energy is heavy and dense, rolls through him at it's own slow pace. Naruto tries to memorize it as best he can, and then does as Kurama says and tries to find the same energy in his bones.

There's nothing at first, just emptiness, and he's about to complain to his bijuu that it's not working like it's supposed to, that he doesn't feel anything– let alone something that resembles the heavy sensation of earth chakra– when he notices… something. It's not chakra, at least not that Naruto can feel, it's more like… the potential of it, something sleeping in the spaces between his ribs.

He reaches for it, tries to draw it from its hiding place, but it remains burrowed, stubborn, entrenched thoroughly in his skeleton. Instead of trying to force it like he would normally, Naruto stops to think. Patience kit. He can imagine Kurama saying. Look at it differently, you might see something new.

Chakra is alive, in it's own way. Kurama had said as much. So it wants something, wants him to do this a certain way. If he wants to draw on it, he has to work with it, not against it.

Strength Kurama had said. The seat of strength.

So how would he draw strength? He tries to remember sparing with Sasuke, to remember how it felt when he pulled up energy he didn't possess, made muscles move that shouldn't have just because he couldn't lose, not again. And he recalls the sensation, how it clawed up from inside him, how he'd had to dig deep.

So Naruto dives, comes at it from underneath, and pulls on it with all his might the way he would if he had nothing left but needed more anyway.

And like crunching rock or breaking bone, something cracks open. Something wakes up. With a rumble that echoes in his ears like the rushing of blood, vibrations roll through him that shake him down to his marrow like an earthquake. It pushes outwards, rushing to his fingertips and through his senses. He smells fresh turned earth and tastes stone dust on the back of his tongue, feels like his bones have turned to mountain granite and that all the force in the world couldn't move him.

~First try. That was pretty impressive, Fishcake.~

Naruto opens his eyes slowly and stares at nothing for a few seconds, bewildered. "What was that?" he asks, flexing his fingers and neck experimentally. Even as the strange power recedes, he still feels… steady in a way he never has. It's like he's found footing that won't shift underneath him, strength he can be sure of.

~You, without any prior chakra training, have just woken your earth chakra system.~

Naruto blinks up at him, both in confusion and an attempt to clear his suddenly shaky vision, because if Naruto didn't know him better, Kurama almost sounds proud.

"That was weird." he says, because he feels the need to voice that sentiment aloud. "Not hard… but weird."

… And Kurama starts laughing at him.

A sharp short dissolves into yipping coyote-like chuckles that Kurama's obviously trying to hide behind a paw but is failing miserably.

"What? What did I say?" he demands. Kurama makes an effort to control himself but doesn't quite manage it the first time, another slew of snickers escaping through his claws.

~You do realize that it can take fully mature shinobi years to activate chakra pathways they weren't born with? You did it in fourteen minutes.~

And it probably takes another fourteen minutes for that to actually sink in, because he's never been good at anything, not really good, but Kurama makes him sound like some sort of…

~Prodigy.~ Kurama says, grinning so wide all his fangs are showing. ~I believe that's the word you're looking for.~

That makes Naruto entirely breathless in a way that has nothing to do with earth chakra.

"What's next?" Naruto blurts. "Water chakra right?" Once can be a fluke– but if he does it twice, three times? He might actually believe it.

Kurama huffs affectionately, heavy enough to ruffle his hair. ~You and all the energy.~ he says, but takes hold of the second sphere anyway, the one that looks like melting crystal. ~But alright.~

Naruto drops back into light meditation and waits.

~Water chakra is the seat of understanding, and is defined by its adaptability and flow.~ Kurama presses the second sphere to the left of the first, into the space over his heart. ~It rests in the blood.~

This power is heavy too, but it's quicker, fluid, harder to grasp. He gets his sense for it, his taste, and focuses his attention on his blood. First he tries to focus on his heart beating, but he gets a different flavor of power from it, tangled and dense, one that doesn't match what he's looking for. So instead he tries to sense the energy in the rush of blood further from it, lower in his chest and higher in his throat. He does find a match there, hiding in the space between beats, but it slips through his metaphorical fingers when he tries to grasp it, avoids him the same way earth did when he sought it out.

Understanding.

But what kind of understanding? Of water? Of chakra?

Of himself?

That question resonates somewhere in his vessels, like a hint.

Close.

What does he understand best? He understands fighting, even if he's not good at it. He understands Kurama, because Kurama is like him in a lot of ways. But he never tried to understand those things… he just did.

But maybe that's it though. Maybe to understand something, you have to let it come to you?

It's worth a shot, so instead of seeking out the power at all, he waits, leaves himself open, and lets the energy come to him when it wants.

It starts as a trickle, the first sign that something's changing, and then it's like the energy can no longer stand the confinement and bursts forward all at once. It crashes through him like a flash flood, pressing against his veins until the pressure grows so high it's nearly painful. It tastes like sea air must, salty and crisp, smells like the petrichor that comes off the sidewalk at the start of a storm. He tingles all over like a rushing river as the chakra washes through his insides.

He feels a little like his apartment had looked that morning, clean and cleared out, like he's been stripped of all those things he didn't want or need but didn't quite know how to throw away.

The sensation, combined with the steadiness still lingering in his bones… it's a strange and heady feeling, and now he gets the sense he's missing pieces of an even greater sensation.

Kurama whistles low. ~The rate at which you're getting the hang of that is mildly disconcerting.~

"Hey, Kurama…" Naruto asks, blinking his eyes open to look at the fox, who seems inordinately pleased with himself. "Are we doing them in this order for a reason?"

Kurama's eyes widen a bit, but then he just grins again, chuckling some more. ~Clever clever fishcake. Yes. There is a method to the madness. Each of the natural elements of chakra have what you could call… an order of stability. Earth Chakra is something of the foundation, which was why I had you wake it first.~

"Like the foundation of a building, right?" Because he's starting to get it, really get it. He's not only understanding what Kurama is saying, he's starting to discover what it means for himself. "It's the most stable, so it's the best to build on top of so that everything else doesn't crash down around it, right?"

Kurama starts snickering again. ~Alright smart guy. If earth is the foundation, then what is water?~

Naruto thinks about that for a moment, scratching absently at his chin. "It's the stabilizer?" He says, because that word fits best. "Or the buffer? It keeps balance, anyways, makes sure one element doesn't override the others."

~How do you figure?~

"Because water can stop fire or lightning or wind in its tracks the way earth can't, and can keep them from interacting badly with each other? It can't stop earth that way, but it doesn't need to, so that's why we did earth first, so water can rest on top of it without being confined and stuff?"

Kurama laughs again, a warm sound, and plops a chakric paw down on Naruto's head to ruffle his hair. Kurama is solid enough that it makes blond go everywhere and stick out like dandelion fluff. Warmth swells so hard in Naruto's chest he almost chokes on it.

~Why all the question marks, Kit? A+.~

Naruto has to take a couple of slightly shaky breaths before he feels comfortable talking without actually bursting into tears. He scrubs his eyes to double check that salt water didn't well up when he wasn't paying attention.

"I got it right?" he says, and even though the words don't shake, his voice is far from steady.

~Sure did.~ Kurama confirms, pinching his nose between his claws to mess with him. Naruto huffs and flails indignantly, and Kurama just laughs some more. Naruto likes it when Kurama laughs like that. ~Water chakra is known as the arbiter, the same way earth chakra is the foundation. It protects the more volatile elements from each other and ensures that all five work in harmony in the system. Of all the elements, water is the only one that is in constant touch with the other four, the same way that blood touches every system in the body.~

"What about the other three?"

Kurama pokes him gently in the forehead with one claw, a soft admonishment.

~Find out for yourself. You're on a roll so far, think you can keep it up?~

Naruto nods, because he really has no words for that, and wonders if this is what it feels like to have an older brother.

"Next is fire?" He asks, and he's proud that his voice doesn't waver this time.

Kurama dips his head in a nod, scooping up the flickering crimson orb in one claw. Naruto takes the cue and drops back into himself again.

He can feel the warmth of the sphere saturate the material of his shirt, lower than the first two–over his navel this time.

~Fire chakra is the seat of will, and is defined by its passion and intensity. It rests in the gut and throat.~

This energy is strange– it's warm, but weirdly empty, and without Kurama to sustain it, it vanishes faster through his system than the others did. He gets enough of a feel for it to know that that it's missing something. He looks for the warmth he felt, but doesn't find it. Instead he finds a cold shadow, something dark and dormant.

Willpower huh?

Kurama had called it intense, but he finds none of that here, just empty chill. But fire needs fuel right? A spark to start it up.

So what feeds will?

And suddenly it's easy. It desires desire, so what does he want more than anything else?

He wants friends, sure, wants family, but what he wants far more than that is the ability to protect them, power enough so that once he has that family, no force in the world could take it from him.

So he takes that desire, and yanks it together into one place, and feeds the fire.

The energy sparks in his stomach, flares fast to life, and roars up to sear his throat until he feels like he could cough up fireballs. It expands like a supernova, pushing heat into every cell. He tastes gunpowder on his tongue and every inhale brings the scent of a forest fire with it.

It makes him feel like he could run for miles, like he should, like any obstacle he could face would be worth it. Combined with the clarity in his blood and the solidity in his bones, he feels like he could take on the world.

He huffs, laughs, shakes his head like a dog shedding water as he comes out of it.

"Whoa, it's like a generator! Or a motivator? Whatever, it gives stuff energy, right?"

Kurama snickers. ~Very good, fishcake. Fire chakra is the amplifier. It's responsible for pushing chakra outwards and increasing the energy that lies dormant in most chakra.~

"Is that why it's in the middle?"

~Yes it is.~

"Cool." Naruto almost wants to train now, to skip the rest and jump right into getting stronger, but he has two more pieces missing, and the idea of missing out on more because he's too impatient to finish this part drowns out the idea. "Wind now?"

~You know the drill.~ Naruto pulls into meditation again and waits for Kurama to give him the fourth sphere. ~Wind chakra is the seat of change, and is defined by its swiftness and unpredictability.~ He presses this orb to the opposite side of his sternum from his heart, at the same elevation. ~It rests in the lungs.~

This power comes to him easy, far easier than the others, twirling in familiar spirals through his system. He hardly needs to go looking, hardly needs to think about it and the answer comes to him. Change is movement, the unexpected, and Naruto likes the unexpected, likes surprises, likes not quite knowing what comes next but rolling with the punches instead. It's how he's gotten through life this far.

It answers the second he calls it up, with the urge to jump when others might stay put, to fall into the abyss just to see what might happen.

It bursts through him like a hurricane, pulling everything around up to dance with it. It sweeps in curling zephyrs of chakra that leave the taste of summer wind on his tongue and air rich with the scent of a coming storm in his lungs.

Combined with the sureness, clarity, and incentive of the previous three elements, he feels like he could stand at the edge of any precipice and fly where others might fall.

Kurama huffs, bringing Naruto out of his head.

~Well that figures.~

Naruto stretches his arms above his head and breathes out a heavy breath. He feels like there's too much air in his lungs. "That one pushes on stuff, makes it move, right?"

Kurama nods again. Naruto really is getting the hang of this.

~Correct. Wind chakra is the dynamo. It shifts everything into motion around it, helps chakra flow the way it's supposed to.~

"Why was it so much easier than the other three?"

~Because it was your 'affinity' so to speak, which doesn't surprise me. Both your parents were that way as well, but just because it's easier doesn't mean you can slack with the other four.~

"Yes Kurama." Naruto drawls, half sarcasm half promise, because he knows. "Lightning now, and then I can learn how to mould it, right?"

Kurama shakes his head. ~Hold a second kid. This one isn't like the others.~

Naruto blinks and looks up at the flickering sphere of black and white where it orbits in circles like an angry moon. "Huh? Why not?"

Kurama brings the orb down so it hovers only a foot or so away from Naruto's nose. It's like looking into a storm, only without the obscuring black of the clouds around it. It seems angry and lost, directionless, thrashing madly to get free of what confines it.

~Lightning chakra is the pinnacle chakra. It is the hardest chakra to master because it possesses the most dangerous properties of all four other chakra types, as well as a nasty property of it own. Most people who claim to have mastered this type of chakra only really know how to mould it and let it loose. Rare is the individual capable of channeling it properly. It is as unpredictable as wind, as damaging as fire, as adaptable as water, and as unmovable as earth. On top of these things, it is capable of stopping life it it's tracks with a touch, capable of stopping a heart, and in the right hands, restarting it.~

Naruto stares at the angry energy, arcing against the borders of the sphere like flashes of a blade, there and gone in an instant. "So it's the strongest then?"

Kurama nods. ~And the most unwieldy. That's why I'm giving you a leg up. Before, I let you determine the nature of the elements yourself in order to better understand them, but this one will not give you two chances. If this gate is forced open, your own body's electrical current could be knocked out of alignment. The rhythm of your cells relies on electricity. One stray discharge could stop your heart.~

Naruto swallows hard. "Yikes."

Kurama's nose ducks in to poke once at his stomach, right over his seal. ~Don't worry kit. I can stop it if that happens, but to do so I would have to shut down your lightning chakra pathways, which would damage them, and I'd rather not have to do that, and I'm sure you'd rather not have that happen.~

Naruto nods. If it's the most powerful kind of chakra, he's going to need to know how to use it. And four out of five would leave a bad taste in his mouth. "So what is it? Where does it come from?"

~Lightning chakra is the seat of power, and is defined by chaos, and by serenity.~

Naruto scratches his jaw. "But wait, aren't they opposites? How can something be both at the same time?"

~That is the question isn't it? That's what makes it so tricky– the duality. Most understand one part or the other, but not both. But without peace the chakra cannot be controlled, and without wrath there is no force behind it. The point of greatest power lies between them, without both, true power cannot be obtained. Do you understand?~

Naruto looks down at his hands. He curls one into a fist, angry and tight and ready to strike, but leaves the other open skyward, relaxed against his knee. Anger is easy, he's known rage for as long as he can remember– rage at the village, at his place in the world, at himself. He's known peace too, wrestling with Kiba or talking with Shikamaru or sitting next to Iruka-sensei at Ichiraku. So he pulls up the fury and tries to mix it with what he felt when he was at peace. For a while he gets nothing, just conflicting sensation, but then something pangs against a familiar ache and a memory from not so long ago comes to mind.

The memory of when he'd run here, tired and afraid and angry and so very very lost. He remembers what he felt when Kurama had asked him why a stranger's hateful words had mattered, remembers how something had shifted inside him, focused down to a few seconds of perfect clarity.

He had still been angry, but he'd been something else too.

"I think I get it." He says, and Kurama doesn't ask him if he's sure. He just floats the sphere of chakra towards him across the short space as Naruto closes his eyes.

~This chakra is known as the catalyst.~ Kurama murmurs, as the sphere sinks into the skin at the base of Naruto's throat. ~It rests in the spine.~

This power flickers, dances in a flash barely long enough for Naruto to get a reading before it's gone. It's strong, a little goes a long way, and what he manages to grab hold of gives him more than enough of a sense for it. He focuses on the energy lying dormant beneath his vertebra. He gets the feeling somehow that this chakra's allegiance is not easily given, but he has the key already, and like the others, he knows what it wants.

This time, when the chakra bursts forward, it doesn't flow through him, it rages, with him and against him all at once. It crackles and surges, spinning static in fractal patterns along his nerves, leaving them raw and overwrought. He feels the wrath in it, but tempered with the calm it becomes honed like a blade– deadly and sharp. It rips through him with so much force it's painful, tears a gasp from his lungs, but when it's through he feels like a waiting thundercloud, dark and dense and charged with power. He opens his eyes to Kurama nosing around him like he's attempting to stiff out injury.

~You okay kit?~ He asks, halfway to a demand.

Naruto nods quickly, because he is, but…

"Does that Chakra always respond so well to pain?"

Kurama sighs, pulling away, but doesn't go far. ~Unfortunately, the things that bring us pain, also tend to bring us strength.~

"Is that why you're so strong?"

The fox's eyes widen, but then soften again to something sad.

~It's why you are.~

It's an evasion, one that doesn't make any sense. "But I'm not strong. Not yet."

~That's not the kind of strength I'm talking about.~

But before Naruto can ask him what the hell he means by that, Kurama sways to his feet and tucks around him, nudging his half-solid snout into his back. ~Enough of that kit, I thought you wanted to train. Up up up.~

"Hold on a sec!" Naruto squawks, tripping to his feet and turning on his bijuu. "I thought you said there were seven types of chakra? Remember? What are the other two? Hey!"

Kurama huffs, curling back around to face him. ~And here I was sure that had slipped right by you.~

Naruto crosses his arms. "Spill."

Kurama chuckles. ~Don't worry, brat. It's easy. Remember how I said nature was balanced by the elemental chakras?~

"Ya." his tone tacks a duh onto the end of the statement. Kurama flicks him in the forehead for his attitude.

~Well, smart-ass, living beings are balanced by another two. Yin and Yang chakra are active in your body whether you like it or not, so no need to go looking for them. They flow throughout your central chakra system and are the types of chakra most ninja rely on.~

"But what do they do? What are they like?" Naruto demands, hopping from foot to foot as he follows Kurama's lazy stride towards the more open part of the clearing.

~Fundamentally, even though they use the same chakra system, the two are very different. Yin chakra is the seat of the spirit, and is defined by emotion. Yang chakra is the seat of the body, and is defined by reality. They're the basis for the use of genjutsu and taijutsu respectively, the same way elemental chakra is used for ninjutsu.

Naruto nods. "I think I get it. Yang chakra works with the body, so fighting and stuff, and Yin works with mind and emotion, and messing with those things, so genjutsu."

~You understood more about that than I'd hoped.~

Naruto makes a face. "I'm really bad at genjutsu."

~We'll work on it.~ Kurama murmurs, nudging Naruto forwards again.

"Wait! One more question."

Kurama sighs again. ~Make it quick, while we still have daylight.~

"What chakra rests in the heart?"

Kurama freezes, bewildered. ~Why would you ask that?~

Naruto rubs the back of his head in nervous habit. "Well, I kinda noticed it first when I was going through the water chakra pathways, and then again with lightning. It kinda feels different, but I sensed chakra there too, just not any there that matched any elemental chakra."

~Fishcake, are you telling me that you accidentally sensed your heart's chakra pathways?~

Naruto blinks. "Uh, yes? Maybe? I don't know."

Kurama taps a knuckle against his chest. ~The heart's chakra system doesn't match any type you know because it doesn't just have one type.~

"Huh?"

~The heart, when it pertains to chakra, has another name. The Nexus. It is the one place in the body through which all chakra passes. The pathways seemed strange to you because instead of one system of chakra vessels, the heart has half a dozen. These pathways are smaller and thinner, but have thousands more branches that overlap and weave together.~

"That makes sense. So it doesn't have it's own resting chakra, because the chakra in it is always moving?"

~Mhm. There's something else about the chakra pathways in the heart you'll find interesting. Unlike your normal pathways, which are set in stone, the chakra pathways in your heart are capable of growth.~

"Like how tree roots grow? To let more chakra through?"

Kurama fixes him with a halfhearted glare.

~You are entirely too good at this. I was going to save this lesson for another day, but I may as well tell you now. Might put things in perspective anyways.~ He draws a circle with his claw over Naruto's heart. ~The more you manage to open into your chakra systems, the more power you'll be able to draw from those systems. The more power you draw, the more strain you put on the vessels in your heart. This prompts those vessels to grow to accommodate the strain. With me so far?~

Naruto nods. Strain makes muscles stronger too– that's how training works, so it makes sense.

~If you grow each of these systems enough– earth, water, fire, wind, lightning, and central– it allows for you to push two types of chakra through at once.~

"Wait wait wait." Naruto crosses his arms in a dramatic X. "You telling me it's possible to use a bunch of elements in one jutsu?"

~Well it's a hell of a lot more complicated than that, there are elements that aren't compatible with one another and other things you'd have to learn, but yes. Essentially.~

"Can we train now?"

~Oh, now you want to train.~ Kurama drawls sarcastically, but nudges Naruto towards the open space by the water anyway.