Four days passed, and nothing happened.
Uchiha Obito had slipped into Konoha and stayed there, moving through it by whatever private geometry Kamui made available to him, and the village had not noticed or had not reacted to noticing, and no incident had emerged to disturb the grove outside the walls where Finn and Black Zetsu were waiting.
Neither of them was particularly concerned. Obito was not a rookie, whatever other assessments one might make of him. A man who had gone round for round with Namikaze Minato and remained functional at the end of it was not someone who would stumble over a routine infiltration. If he'd made a critical error, they would have heard about it. Konoha's level of response to a genuine intrusion at that tier would not have been subtle.
So they waited, and they talked, and the days were, against all expectation, pleasant.
Black Zetsu had accumulated a great deal of time and had spent most of it in calculation. Planning, maneuvering, managing the long trajectory of a project that measured its timescale in human generations. Conversation of the kind that had no operational purpose, that existed purely because two people were in proximity and found each other's company interesting, was something he had not had much of.
He found he didn't mind it.
Finn was good to talk to in ways that were difficult to itemize. He asked questions that were genuinely curious rather than pointed. He didn't perform reactions. He absorbed information and sat with it and occasionally returned something unexpected from the far side of the consideration. Black Zetsu had known a great many people across his long existence, and the ones who could actually think rather than simply accumulate knowledge were rarer than the raw numbers of the population suggested they should be.
Beyond the conversation itself, Black Zetsu was aware of doing something he rarely did with anyone: reassessing.
Uchiha Madara had been a tool from the beginning. A brilliant tool, a necessary one, shaped over decades into something that could serve the plan's requirements, but a tool in the precise sense that his function was defined entirely by its usefulness to an end he didn't actually control. He would not survive the plan's completion. That was always the case. Black Zetsu had never thought of him in terms that extended beyond that frame.
Finn was different, and the difference was compound. He was powerful in ways that were not yet fully apparent even to people who had already been surprised by him. He was intelligent. He pursued things for his own reasons and was honest about what those reasons were, which was unusual. And he was, Black Zetsu thought, someone who might be interested in what came after the plan's completion, rather than someone who simply didn't survive to see it.
His mother would need capable allies when she returned to the world. People who could serve as instruments of the new order rather than obstacles to it. People whose own ambitions could be accommodated within a larger structure.
The deception involved in the current arrangement was real but not final. That could be changed. If the final arrangement was one where Finn genuinely understood what was being built and chose to be part of it, and if what he wanted could be provided within that context, then there was nothing to deceive him about.
Black Zetsu filed the thought for later consideration and paid attention to the conversation.
"All right, what exactly is Yomi?" Finn asked, turning the fish on the improvised grill over a small fire. He reached for the pipe at his waist, took a pull, exhaled slowly. "I've been working on soul-related things lately. I'm curious about the hierarchy. The King of Yomi, the Shinigami, the God of Death. What kind of existence are they?"
Black Zetsu considered the question. He ran through it for anything that touched on things he'd prefer to keep private, found nothing of consequence, and answered.
"Yomi is not worth much attention on his own. He's a creature, essentially. He broke free from the normal constraints of life and death, which sounds impressive until you understand the mechanism." He paused. "Do you have a clear sense of what the tailed beasts fundamentally are?"
Finn took the fish off the grill and looked at it. "Chakra aggregates. Natural chakra that took on character and will over time. They don't die in any final sense because their substance can reconstitute, and when they're destroyed the chakra disperses and eventually collects again."
"Correct. Yomi operates on a similar principle, though the mechanism is different. He's a combination of soul energy and accumulated malicious spirit. The soul component alone can't escape the cycle of death and rebirth. But the malicious spirit, the condensed negative force that this world generates, gives the soul something external to anchor against. So he persists. He can be sealed, not killed, because the underlying material just reconstitutes the way tailed beast chakra does."
Finn chewed, thought. "And the malicious spirit itself. What is that exactly?"
"Dark energy produced by negative emotion. Hatred, resentment, envy, cruelty. Any creature capable of feeling generates trace amounts of it continuously. It has existed since the first creatures existed. You could call it a law of this world's operation: life produces its own shadow." Black Zetsu's voice was level, neither approving nor condemning, the tone of someone describing weather patterns.
"That's deeply unpleasant," Finn said, without particular distress. "And Yomi's tapped into it as a survival mechanism." He looked down at the Shindokutō at his waist. "I'd heard there was something sealed in the Land of Demons along those lines. Didn't know the specifics."
Black Zetsu's attention had already moved to the sword. He looked at it for a moment, in the way he looked at things when he was trying to identify something.
"Your sword," he said. "It contains evil energy. A significant amount." He paused. "What's more interesting is that you don't seem affected by it. Extended proximity to that kind of force normally produces changes in the person carrying it. Distorted thinking. Instability. It's gradual, but consistent."
"Maybe I'm already distorted," Finn said.
Black Zetsu paused.
Finn laughed. "I'm joking. Mostly."
He hadn't thought about it in detail before. He'd noticed, when he first took up the Shindokutō, that it had produced discomfort. He'd attributed the eventual resolution to the sword accepting him as its owner, the common frame for that kind of weapon. Apparently the frame was incomplete. Something in him had processed the evil energy and continued to process it without the expected consequences.
He filed it as a property of himself he didn't fully understand yet and moved on.
"Yomi is small scale," he said. "What you described suggests there's something else. Something that operates at a larger scale and also draws on this dark energy."
"There is. It calls itself a god." Black Zetsu thought for a moment. "I don't know whether it has a name in any meaningful sense. It has existed for a very long time, comparable in duration to the entities I'd classify as genuinely divine. But its nature is different. It has no self-will left, which limits it. What it can do is function as a conceptual force."
"What concept?"
"Immortality. Specifically, physical immortality. It seems that at some point it had genuine believers, people who worshipped it and received something in exchange. The exchange was that their bodies became unkillable by conventional means."
Finn thought about this. Hidan. The man had been a practical problem in the original timeline precisely because the usual means of resolution didn't apply. Removing the head hadn't been sufficient. The workaround had involved separating the head from the body by a sufficient distance and waiting for the body to stop working from lack of maintenance.
"That's physical only," Finn said. "The soul doesn't benefit."
"Correct. The soul remains fully mortal. If the soul dies, the body continues without it."
"So the body becomes a problem that outlasts the person." Finn set down the fish. "That's not immortality, that's a specific kind of horror with religious branding."
Black Zetsu said nothing, which seemed to indicate agreement.
"The Shinigami and Yama are more interesting," Finn said. "Tell me about them."
He meant this in a way Black Zetsu couldn't fully know. The information in Orochimaru's soul research notebook, cross-referenced against what Finn already understood from his own knowledge, had produced a conclusion that he carried carefully: the entity referred to in the Naruto world as King Yama, as the ruler of the Pure Land, as the supreme judge of the dead, was Kaguya Otsutsuki. Not an analogy, not a coincidence of titles. The thing the Human Path technique summoned, that ancient and terrible presence at the center of the underworld's structure, was Black Zetsu's mother in a form no one had correctly identified.
He sat and listened to Black Zetsu explain it.
"My honest answer is that I'm not fully certain," Black Zetsu said, with unusual candor. "What I believe, based on evidence I've accumulated over a very long time, is that the Shinigami and Yama were not always what they are now. I think they were once souls. Living people, or something like living people. But they were souls of extraordinary strength, and over an enormous span of time, after their deaths, they became... part of what they inhabited." He paused. "The Pure Land assimilates what enters it. Most souls pass through and move on. But something with sufficient strength and no remaining trajectory might not move on. It might stay, and over enough time, it might stop being a distinct thing and start being the place itself."
Finn turned this over.
"So they're too large to be people anymore," he said.
"They assimilated with the structure of the Pure Land across spans of time I can't precisely quantify. They became conceptual forces rather than individuals. The Shinigami still operates, still functions in specific ways when invoked, but whether there's a self behind it in any meaningful sense, I can't confirm." Black Zetsu was quiet for a moment. "What I can say is that the soul capable of reaching that kind of scale is something I've only encountered in theory. I don't know what the threshold looks like or what happens at the boundary."
"The soul too powerful," Finn said, half to himself.
He felt something in the formulation, some edge that connected to something else, but the connection wasn't completing. The Spiritualization Secret Art and what it was building in him. Black Zetsu's observation about the Shindokutō's evil energy not distorting him. The soul-body compatibility limit that Orochimaru had described from the Kato clan's accumulated experience. The two extremes: a soul so depleted it could no longer support the body, and a soul so developed it might exceed the body's capacity to contain it.
And above both of those, at some scale he couldn't see yet, something that had grown past the category of individual entirely.
He sat with the thought.
Something at the edge of the grove moved. The space distorted in a way he'd become familiar with, the particular geometric wrongness that preceded Kamui's resolution. Uchiha Obito stepped back into the visible world, and simultaneously, from the bark of a tree on the other side of the clearing, White Zetsu flowed out of the wood like something poured out of a vessel.
Four days in Konoha. A signal in the return.
Finn looked at Obito, at White Zetsu, at the quality of their movement, and set aside everything he'd been thinking about.
The time, apparently, had come.