The silence after Finn's suggestion ran for several seconds.
Then Sasori said, with the careful tone of someone testing the structural integrity of an idea before committing their weight to it, "It might be possible. In theory."
Finn nodded slowly. Then he put his hand on Sasori's shoulder with what felt like genuine feeling.
"I misjudged you," he said. "I'll admit it. When I first heard about the human puppet technique, I thought the ceiling was already in view. One man, however skilled, building a collection of powerful puppets over time. It's impressive but it has a horizon. I was wrong. What you've actually built is something closer to a conversion system. Every powerful enemy becomes a permanent asset. There is no ceiling on that model, not in principle."
Sasori looked at him with mild suspicion, as he always did when Finn's tone shifted toward something resembling sincerity.
"So when the time comes," Finn continued, "we open Hashirama Senju's grave, you study how the Sharingan situation resolves with Kagami here, and then once the Sharingan problem is solved we look into the Uchiha Madara question. Madara is not going to live much longer by any reasonable estimate. He's been in hiding for decades, his body is running out of whatever it's running on, and when he finally goes, you should be positioned to make use of it." He paused, working through the implications. "The two combined: Wood Release at full original scale and whatever Mangekyō ability Madara has been sitting on for sixty years. Sasori, that is not a 'powerful puppeteer' outcome. That is a walking natural disaster."
Sasori was quiet for a moment that carried something genuine in it, as though the argument had landed somewhere rather than deflecting off his usual armor.
Then he said, "There are problems."
"Of course there are problems."
"The bodies would need to be in usable condition. Without preservation treatment, bodies deteriorate. Hashirama Senju has been dead for decades. If what remains is bones, or advanced decomposition, the puppet technique cannot work with it. The cellular structures need to retain enough integrity for the technique to interface with them." He paused. "And Madara, even if he dies soon, I would need to reach the body quickly. Before the usual processes begin."
"Logistical problems," Finn said. "Solvable with planning."
"They are not small problems."
"I didn't say they were small. I said they were solvable." He removed his hand from Sasori's shoulder. "The Hashirama question we find out about when we go look. If the body is viable, we proceed. If it's not, we know. The Madara question we plan for in advance: when the time comes, we need to be close enough and fast enough to act before anyone else does."
Sasori said nothing for a moment. Then, with a quality in his voice that was somewhere between resignation and recalibration, he said, "You really are committed to this idea."
"I think it's the correct idea," Finn said. "Which is different from being committed to it for its own sake."
Sasori turned back to the table.
"Then there is another conversation we should have. Because something you said concerns me."
"The Impure World Reincarnation."
The words came out of Finn before he had finished choosing them, because the look on Sasori's face, the slight freezing in his movements from a moment earlier, had already told him what the relevant subject was.
Sasori's hands went still. "What is it?"
"A forbidden technique. Developed by the Second Hokage, Tobirama Senju. It can, within limits, bring the dead back." Finn watched Sasori's face carefully. "Not restore life. More like... compel the dead to inhabit a living vessel and respond to instruction. The soul returns to a body constructed from another person's living tissue, sealed with a talisman. The resurrected person has their full abilities intact. The technique gives the user access to whatever they were capable of in life."
He paused.
"The technique Tobirama developed is still in its early form. It has limitations. It's not widely known. But the concept exists, and someone ambitious enough with the right theoretical foundation could develop it considerably further. What you described with the puppet technique, the idea of accumulating powerful adversaries and turning their strength into your own, this technique achieves a version of that. Potentially at greater scale."
Sasori was quiet. The quality of his stillness had changed.
"I'm not suggesting you pursue it," Finn said. "I'm telling you it exists because you should know it exists, and because the fact that it exists says something about what this world is capable of. Techniques that bridge the boundary between life and death are not theoretical in this world. They are engineering problems."
A long silence followed.
Then Sasori said, softly and to no one in particular, "Those who play with life and death will eventually be played with in return."
His voice had lost the flatness that it usually carried. Not broken, not grieving exactly, but holding something that had been compressed for a long time under the professional surface.
His puppetry was transgressive, clearly. He had taken the bodies of people he had killed and converted them into tools. He had converted himself. He operated on the margins of what most people would categorize as acceptable even in the ninja world's fairly permissive moral landscape. He did not, as far as Finn could tell, lose sleep over most of this.
But the soul was a different category. The animation of dead tissue through chakra and mechanics was one thing. Calling a soul back across whatever boundary separated the living from the dead was something else. His puppets did not contain their original occupants. They contained material that had once belonged to those occupants, reshaped into something new. There was a distinction there that mattered to him in ways he had never articulated and probably never would.
Finn thought about Sasori's parents. Killed during the Second Shinobi World War, at the hands of Hatake Sakumo, Kakashi's father. Sasori had been very young. His grandmother Chiyo had raised him, and had loved him, and had not been able to fill the specific space that had been emptied. He had made puppets of his parents eventually. Not to bring them back. To keep something of them. To give the grief a shape he could control, which was the closest thing to resolution that a person of his specific temperament could access.
He had had opportunities to attempt something like genuine resurrection, in his later years, working alongside Orochimaru. He had not taken them. The reason was not inability. The reason was the same line he had just invoked: there were things you did not do, and for Sasori, calling souls back was one of them. The body was fair game. The soul was not his to touch.
It was a bottom line that Orochimaru did not share, which was probably the clearest statement of why the two of them had never been comfortable working together for long.
Finn let the moment pass without pressing it. He had understood what he needed to understand. The Impure World Reincarnation was not a direction Sasori would go, which meant it was a direction that would remain in someone else's hands. Orochimaru's, currently. Kabuto's eventually. Both of those were problems for a different season.
Sasori pulled his attention back to the table. The subject was closed. His hands moved again, returning to the work with the precision of someone who found the work itself steadying.
Finn watched for a moment, then said, "While you're working on that: would you mind if I spent some time with the Sharingan? Studying it, not removing it. I have reasons to be interested in what it can do."
"I'm studying the Sharingan," Sasori said, with the patience of someone addressing an obvious problem. "That's what I'm doing right now."
"Study it with one eye, then."
A short silence. "Why the Sharingan specifically? You handled Kagami without any apparent difficulty."
"Because Kagami wasn't trying to trap me with it," Finn said. "He was using it as a targeting system and a reaction enhancer. That's not the part of the Sharingan I'm interested in."
Sasori looked up. Something had caught in his expression that Finn recognized as the sharpening of a perceptive mind running backward through a sequence of events. "When Kagami opened the Mangekyō," he said slowly, "you moved your eyes. You stopped looking at his face directly. That was deliberate."
"Yes."
"You know what his Mangekyō does."
"I had a strong suspicion. I wasn't willing to confirm it experimentally."
Sasori looked at him for a long moment. "You know things about the Uchiha clan that no one outside it should know. You knew Kagami had the Mangekyō before he used it. You knew there was a higher level of Sharingan before he activated it. You claimed earlier to have seen Uchiha Madara's eyes, and when I pointed out that Madara died before you could possibly have been born, you said I should not make assumptions about your age."
Finn said nothing.
"How old are you?"
Finn stroked his chin. He looked at the ceiling. He produced an expression that was somewhere between evasive and genuinely amused. "Older than I look," he said. "Considerably older. That is not a deflection; it is the actual answer. The appearance is a result of certain properties of my bloodline limit and the way this world has been interacting with them. What you're seeing is not the full picture." He paused. "I'll say this much: I have not been in this world long. But I know it better than my time here would account for. You are not wrong to notice that. You would be wrong to press further."
Sasori looked at him for a while with the particular expression he produced when he was filing information under "unresolved but noted" rather than "understood."
Then he turned back to Uchiha Kagami and said, "Pay attention. I'm starting now."
Finn moved closer to the table, keeping a careful distance from the eyes, and watched.