Sukuna held his hands six inches apart and pulled.
The chakra between his palms split. The warmth of physical energy drifted left and the hum of spiritual energy drifted right, and for a moment the two halves hung there, a faint gold shimmer on one side and a pale blue on the other. The space between them darkened and the temperature dropped by several degrees, and Konan, who sat closest, pulled her cloak tighter around her shoulders. The two energies strained toward each other, and Sukuna held them apart through sheer control, and the tension between them produced something cold and colorless that settled into his palms and made the grass beneath his feet go brown and brittle in a perfect circle.
"That," Sukuna said, "is Negative Chakra."
Fourteen people sat in a rough semicircle on the training field behind the Akatsuki compound. Yahiko sat at the center of the group with his legs crossed and his elbows on his knees, leaning forward. Konan sat to his right with a sheet of paper in her lap and an ink brush in her hand, taking notes in a shorthand that Sukuna had never been able to read. Nagato sat to Yahiko's left, slightly behind him, with his red hair hanging across his face and those ringed eyes watching through the gaps. The remaining eleven were a mix of fighters and support staff, sixteen to thirty-something, and most of them looked lost.
A young man named Daisuke raised his hand. He was the primary field medic, twenty-two and stocky, with a scar across his chin from shrapnel he'd caught during the war. He had steady hands and a good head for anatomy, and Sukuna liked him well enough, which was more than he could say for most people.
"Could you do that again?" Daisuke asked. "Slower, maybe? I lost it at the part where the two energies, you know, actually separated."
Sukuna let the Negative Chakra dissipate and the cold faded. The dead grass stayed dead. He brought his hands together and then apart again, and this time he slowed the process to a crawl, drawing the separation out across several seconds. The gold shimmer appeared on his left. The blue appeared on his right. The gap between them widened.
Daisuke squinted and leaned forward until he was practically on all fours. "I can sort of see the colors, I think. But I don't understand what you're actually doing with your network. Are you running the energies through different pathways? Splitting the flow at a junction point?"
"No. The split happens everywhere at once. Every node, every pathway, simultaneously. You're not routing the energies through separate channels; you're forcing the components apart within the unified flow itself." Sukuna paused. This was the part where everyone got lost. "Think of it like this. Your chakra is water. Physical energy is the hydrogen. Spiritual energy is the oxygen. They exist together as a single substance. What I'm doing is pulling the hydrogen and oxygen apart while the water is still flowing through the pipe."
Daisuke sat back on his heels.
"Yeah," he said. "That makes sense. I just have no idea how to actually do it."
A woman named Sora crossed her arms. She was late twenties with short dark hair, one of the Akatsuki's better fighters. "I mean, every instructor I've ever had said that physical and spiritual energy can't exist separately inside a living person's network. The whole point of chakra is that the two energies are fused. It's like trying to separate the flour from the bread after it's been baked."
"They can exist separately," Sukuna said. "I do it every time I use the technique. The fact that nobody else has managed it doesn't mean it's impossible; it just means it's very difficult."
"How difficult are we talking?" Yahiko asked.
"I was dying when I figured it out. Both femoral arteries were open and my abdominal wall was split and I had maybe thirty seconds of consciousness left." He shrugged. "The desperation opened something in my network that I hadn't been able to access through meditation or training. The separation just happened, and the Negative Chakra came out of it, and I used it to heal myself and then Wasuke."
The semicircle went quiet. A few of the newer members looked at each other. Yahiko's jaw tightened, and Konan's brush paused on the page.
"Try it," Sukuna said. "All of you. Sit, close your eyes, and feel the two component energies inside your chakra flow. Physical is warm. Biological. It comes from your body's cellular processes. Spiritual is something else; it comes from your mind and your will. They feel different if you pay attention. Find the boundary between them and try to widen it."
Fourteen people closed their eyes. The training field went quiet except for the rain, which had been falling since before dawn.
Sukuna felt their chakra, all fourteen signatures, and watched for any sign that someone was making progress.
Nothing happened. Their chakra continued flowing, the physical and spiritual components bound together so tightly that the boundary between them was nonexistent. A few of them managed to sense the two components, their faces tightening with concentration.
Daisuke's face scrunched up until it went red, and his chakra responded by flowing faster and denser. Sora's approach was more careful, but her chakra didn't budge. The rest of the group produced similar results.
After ten minutes, Sukuna told them to stop. Most of them opened their eyes looking a little dazed.
"Nobody even came close," Sora said. She didn't sound surprised.
"No," Sukuna agreed.
Nagato opened his eyes last. His ringed pupils caught the gray light, and Sukuna sensed him focusing before he spoke. He'd been watching the demonstration with those eyes the entire time.
"I saw the separation," Nagato said quietly. "When you pulled the energies apart, I could see the individual flows. The physical energy has a different wavelength from the spiritual energy. They vibrate at different frequencies, and when they're combined those frequencies merge into a single harmonic. What you did was introduce a dissonance that forced the two frequencies apart."
Sukuna looked at him. "And?"
"And I have absolutely no idea how to replicate it," Nagato said. He pressed his palms together and concentrated, and the Rinnegan's concentric rings pulsed slightly as he turned his perception inward. His chakra stirred and the flow accelerated.
And then he tried to push them apart. Sukuna saw the attempt through his own perception; a careful and precise application of will directed at the junction between the two energy types. Nagato had the understanding and could see what needed to happen. His eyes gave him the blueprint.
But his hands couldn't build it. The control required to affect every node and pathway in his body at once exceeded what he could manage. The attempt lasted maybe three seconds before the two frequencies snapped back together and Nagato exhaled through his nose.
"I can see it," Nagato said. "I can see exactly what you're doing and why it works. But the control required is beyond me. I just don’t have the precision to separate the two energies across every pathway simultaneously. I'd need to individually control thousands of junction points at once, and even with the Rinnegan, I can manage maybe a dozen before the rest collapse."
"Wait, thousands?" Daisuke looked between Nagato and Sukuna.
"More than that," Nagato said. He sounded tired. "Every junction point. In his entire body. All at once. The separation has to be total or it doesn't produce the Negative Chakra."
The semicircle absorbed this.
Yahiko unfolded his legs and sat up straighter. He'd been quiet through the demonstration and the failed attempts.
"Okay. So the technique is real and it's incredibly difficult and maybe nobody here can do it. That's clear enough." He gestured at Sukuna. "But I want to understand what we'd actually gain from it. Because we already have healing jutsu. Mystical Palm. The whole medical ninjutsu toolbox. Those techniques work; they save lives every day. So what does Negative Chakra give us that conventional healing doesn't?"
Sukuna held up his left hand.
He drew the katana with his right.
The blade came through his left wrist in a single clean motion. His hand separated from his arm and dropped to the wet grass beside his knee, fingers still twitching. Blood sprayed from the stump in two arterial jets that soaked the earth in front of him and spattered the boots of the nearest observers.
Daisuke lunged forward with his hands already glowing green with medical chakra. Sora swore and reached for a pressure bandage from the kit at her hip. Three of the newer members scrambled backward. Konan's brush stopped on the page and her eyes went wide, and Yahiko was already on his feet.
Nagato didn't move. His ringed eyes watched, and the rings pulsed.
Sukuna looked at the stump of his left wrist, where two severed arteries pumped blood in rhythmic jets that weakened with each beat, and he pulled the physical and spiritual energies apart inside his network and the Negative Chakra bloomed in his core and flowed down his arm to the wound.
The bleeding stopped. Not slowed; stopped. The arterial jets cut off mid-pulse, and the blood that had been flowing reversed direction and drew back into the severed vessels. The cut surfaces of the wrist moved. Bone grew from the stump, white and glistening, and formed the carpal structure in sequence, each piece clicking into place as the joint rebuilt itself. Metacarpals followed, five shafts extending outward into finger joints. Tendons appeared and threaded themselves through the developing hand. Muscle bloomed around the framework, pink and dense, layering itself into place. Blood vessels branched and spread. Nerves grew last, fine white threads tracing their paths through the new tissue.
Skin sealed over the whole thing in a wave that traveled from wrist to fingertips, and Sukuna flexed his left hand and felt every finger respond.
The entire process took about eight seconds.
He held the hand up and turned it in front of Yahiko. The rain landed on the new skin and ran down his fingers and dripped from his knuckles. There was no scar, no discoloration. Nothing.
"Can your healing jutsu do that?" Sukuna asked.
Nobody said anything. Daisuke stood frozen with his hands still glowing green, the medical chakra humming uselessly against his palms. Sora held the pressure bandage in white-knuckled fingers. Yahiko's mouth was open, and Konan's brush was dripping ink onto her notes.
Nagato sat perfectly still. His Rinnegan was active, the rings pulsing in a slow rhythm.
"No," Daisuke said finally. His voice came out rough. He looked down at his own glowing hands and the light faded. "Medical ninjutsu accelerates the body's natural healing processes. It can close wounds, mend bones, repair damaged tissue. But it works within biological limits. A severed hand is just gone. The cells at the stump can't replicate an entire complex structure from scratch; they don't have the template. You'd need months of surgical reconstruction and even then the functionality would be partial at best."
Sukuna sheathed the katana and picked up his severed hand from the grass. The fingers had gone pale and stiff. He examined it for a moment and tossed it into the undergrowth at the field's edge. A pointless thing now.
"Negative Chakra doesn't accelerate natural healing," Sukuna said. "It reverses damage. Acceleration just makes your body work faster within its existing capabilities. Reversal means the damage itself is undone. The tissue doesn't grow back; it was never destroyed. That's why the regeneration is perfect. There's no scarring, no loss of function, no limitation based on injury severity. A cut heals the same as a severed limb heals the same as a destroyed organ."
He looked at Yahiko. "That's the advantage."
Yahiko sat back down slowly. He ran both hands through his wet hair and stared at the ground between his knees for a few seconds. Then he looked up. "And you're telling me that nobody in this group can learn to do it."
Sukuna looked at the faces around the semicircle. Fourteen people had tried and failed to produce even the faintest separation of their component energies. Nagato could see the technique with perfect clarity and still couldn't perform it. And Wasuke had been trying for months and had gotten no closer than he'd been on the first day.
"Maybe," Sukuna said, shrugging. "It took me being seconds away from dying to figure it out, and even then it might've just been something about the way my network is built. Wasuke's tried everything I've tried and hasn't gotten it, and his network is identical to mine."
Wasuke sat at the far end of the semicircle with the yari across his lap and his back against a fence post. He nodded.
"Yeah, I've been at it for a while now," Wasuke said. He rolled the yari's shaft between his palms. "I can feel the two energies. I can tell them apart. I can even sense the boundary between them, which is more than I managed when we started. But every time I try to push them apart, the whole thing just snaps back together. It's like trying to use your right hand to grab your right elbow; the tool you need is the thing you're trying to reach. The control required to separate the energies has to come from the energies themselves, and they don't want to be separated."
"It might just be one of those things," Sukuna said. "Some techniques require specific conditions or specific physiology, and you either have them or you don't. I'm not going to claim that nobody else can ever produce Negative Chakra, but I'm also not going to promise that practice alone will get you there."
Yahiko nodded and let the subject go. He turned to Konan, who was scanning her ink-spattered notes. "Mark it as a theoretical capability. Something we're aware of and keep working on. If anyone shows an aptitude for the separation, we prioritize their development."
Konan nodded and started writing.
The group broke apart as people stood and stretched. Daisuke cornered Nagato and started asking whether the Rinnegan could be used to guide someone else through the separation process in real time, and Nagato said he didn't know but was willing to try.
Sora stopped beside Sukuna on her way toward the compound.
"That was the most disturbing thing I've ever seen anyone do to themselves on purpose," she said. "And I watched a man pull a kunai out of his own eye during the war. Voluntarily."
"Context helps," Sukuna said.
She snorted and walked off.
The rest of the afternoon looked the same as it had for months. Small groups of Akatsuki members gathered across the compound and the training field and the covered walkways, trading knowledge.
Wasuke stood at the field's northern edge with Konan, demonstrating the principles of his anti-genjutsu seal. Konan watched his hands with close attention as he traced the detection array symbols on a practice scroll, her own origami creations arranged on a flat stone beside her in neat rows. Her paper manipulation technique overlapped with fuinjutsu in ways that had surprised both of them, and she and Wasuke had spent weeks trading ideas about how written symbols could encode persistent functions. The anti-genjutsu seal's monitoring system interested her specifically because it operated continuously without active maintenance, a quality her paper constructs currently lacked.
Sukuna sat under the covered walkway and watched the exchanges while oiling his katana. Across the courtyard, a chunin-level fighter named Hideo showed three younger members a wind-chakra shaping exercise that he'd adapted from a technique his former village had classified as restricted. The classifications didn't mean much to Hideo anymore, and he walked the students through the hand positions patiently. Near the well, Nagato sat cross-legged and demonstrated a gravity manipulation technique to Daisuke and two others, a minor application of the Rinnegan's capabilities. The technique let him alter the weight of objects within a small radius, and the applications for field medicine were obvious; reducing a patient's effective body weight during evacuation, increasing pressure on a wound without physical contact.
Yahiko moved between the groups, checking in and asking questions and occasionally sitting down to learn something himself. Sukuna had watched him study Wasuke's spear forms for an hour the previous week and then adapt three of the movements into his own swordsmanship, and the adaptation was clean enough that Wasuke noticed.
Of course, the knowledge sharing was the thing Sukuna had expected least when they'd joined, and it was the thing he valued most. The shinobi villages hoarded their techniques and classified them and restricted access based on rank and loyalty and politics that had nothing to do with whether a given person would benefit from learning a given skill. The Akatsuki didn't operate that way. Information flowed freely because Yahiko believed that shared capability made the whole organization stronger, and the results bore him out.
Sukuna's own contributions had been significant. He'd taught the Body Flicker variants to anyone whose chakra control could handle them. The partial limb surge worked for most of the fighters, and even those who struggled with the isolation component improved their base speed through the attempt. The brain acceleration remained beyond everyone except Nagato, who'd managed a brief and low-level version during a sparring session last month before mental exhaustion forced him to stop. His eyes, as it turned out, constantly eroded his stamina.
In return, Sukuna had learned things he couldn't have found on his own. Hideo's wind shaping had given him ideas about how to reduce the visibility of his Kamino technique, compressing the flames inside a shell of wind chakra that contained the light and heat until the moment of impact. Konan's paper manipulation had inspired new approaches to his fuinjutsu research, particularly the idea of using multiple small seals working together instead of one large one. And Nagato's gravity techniques had gotten him thinking about whether Negative Chakra could affect more than just biological tissue.
Wasuke contributed genjutsu instruction that had transformed the Akatsuki's defensive capabilities. Nearly every member now had a basic understanding of how illusory techniques operated and how to recognize and disrupt them. The full anti-genjutsu seal remained Wasuke's most closely guarded creation, restricted to people he trusted personally, but the underlying detection principles had been taught broadly enough that the organization's vulnerability to sensory manipulation had dropped significantly.
The rain continued and the training field turned soft and muddy. Sukuna finished oiling the katana and slid it back into the scabbard and set it beside him on the bench. Across the compound, lanterns lit up in the windows of the residential buildings as the afternoon darkened into early evening, and the smell of cooking rice drifted from the kitchen, and the sound of conversation mixed with the rain into something that sounded, if Sukuna was being honest with himself, kind of like home.
Wasuke appeared beside him and sat down on the bench. His brother had finished the seal demonstration with Konan and had rain in his hair and ink on his fingers.
"Konan figured out how to make the detection array self-sustaining," Wasuke said. He held up a small square of folded paper with symbols drawn on it in precise lines. "She embedded it in the paper itself. The fold pattern creates a physical resonance that mimics the chakra circulation I was using to power the seal. It's honestly kind of brilliant."
Sukuna took the paper and examined the folds. The symbols were Wasuke's, but the architecture was Konan's, and the combination produced something neither of them would've built alone.
He handed the paper back. "Good."
Wasuke tucked the paper into his belt and leaned back against the wall and watched the rain, and they sat together without talking. “Do you think we’re doing good?”
“What do you mean?”
“I mean… do you think Akatsuki is actually making a difference in the world?”
“I feel like I’m not the right person to ask that.”
“No. You’re not biased. I think you’re the best person to ask.”
Sukuna huffed and turned to the rain again. “Individually, perhaps. It would be dishonest to say that you guys haven’t helped anyone. But the bigger picture? You’re basically trying to paddle using a knife? Are you displacing some water? Certainly. Are you displacing enough of it to move the boat forward? No.”
“What are you saying?”
Sukuna shrugged. “I’m saying that you’re trying to cure the individual symptoms of a far larger problem. And that problem is the very nature of the world itself, where the strong devour the weak. It hasn’t changed. And it will never change.”