Hii Kōri didn't linger in the "warehouse" full of hanging experimental subjects. He walked past the Konoha ninja who began struggling and cursing violently at the sight of him and headed straight for a room deeper in the dungeon.
Rashōmon, dwelling in his shadow, emerged. Its shadow rippled, silently "swallowing" one male and one female prisoner, then returned to its original shape.
Pushing open the door, Hii Kōri was greeted by a room so clean it was almost empty. The walls and ceiling were made of easily cleaned materials. Aside from a table in the corner, there was no other equipment.
He took several notebooks and a tape recorder from the scroll on his wrist and set them on the table. The worn notebooks contained his research notes on the Spirit Transformation Technique and Impure World Reincarnation, along with the prisoners' data. The fresh notebook was for recording the upcoming experiments.
Next, he set up various cameras around the room, ensuring every angle would capture every detail of what was about to happen.
While he set up the cameras, the spirit-thread nerves in his hair picked up brushes and began drawing intricate sealing formulas on the floor in the center of the room.
With everything ready, Rashōmon stirred and "spat" the male prisoner into the center of the formula.
The prisoner had already been stripped of all clothing, tightly bound in a half-kneeling position that left him barely able to move. A wad of cloth was stuffed in his mouth, preventing him from uttering even a single curse.
"Recording started."
Hii Kōri pressed the record button. The tape began to turn.
"Date: April 13th. Hii Kōri begins first Impure World Reincarnation validation experiment log."
Speaking in a steady tone, he took out a small test tube containing a few milliliters of dark red blood a blood sample from Tsunade.
Carefully, he poured the blood into a small pile of specially prepared soil, mixing it thoroughly. Then he gathered the soil and pressed it onto another scroll, similarly marked with formulas.
Rat, Snake, Dog, Dragon hands pressed together.
"Summoning Technique: Impure World Reincarnation."
Then, nothing happened.
The scroll with the soil did not connect to the formula on the floor. The bound prisoner in the center remained unchanged.
"Experiment 1: Using target 'Tsunade's' blood as medium, 'Ōtani Makoto' as vessel. Technique failed to activate."
Rashōmon deftly cleaned up the discarded scroll and soil. Hii Kōri dictated the results into the recorder while writing his analysis in the notebook: "Living persons cannot be summoned."
Next, he took out a second sample several strands of hair in a sealed bag. They were remnants from his foster father Matazaburō, who had been absent for years.
Same process, same technique. Same lack of response.
"Experiment 2: Using target 'Matazaburō's' tissue as medium, 'Ōtani Makoto' as vessel. Technique failed to activate."
After recording this, Hii Kōri paused the recording and the cameras. Then, using his finger as a blade, he cut open his palm, letting his warm blood mix with fresh soil.
"Impure World Reincarnation."
He pressed his hands together, softly repeating the procedure, and activated the technique.
This time with himself, a living person, as the target a clear anomaly appeared.
The soil mixed with Hii Kōri's blood seemed to come alive. It turned into a filthy mudflow that rapidly crawled up the prisoner's body, accompanied by a spine-chilling rustle.
The mud covered the prisoner's legs, his torso, and began spreading toward his face. The gagged man let out a miserable, muffled groan. His body temperature was dropping precipitously.
The mud that had swallowed him seemed on the verge of coalescing into some vague humanoid shape. But just as the clay figure was about to form, the spreading mud suddenly dried completely.
Losing all cohesion, the mud crumbled into countless fragments. All that remained was the prisoner, lying in his own filth, all strength drained by the bone-chilling cold that had tried to seize his very life force, trembling helplessly.
"…Just as I thought."
Hii Kōri rubbed his chin, showing no surprise at the scene.
Having studied Impure World Reincarnation through Tsunade's "eyes" and even attempted it himself, he certainly knew the common knowledge that a living person's soul could not be summoned.
But precisely because he had studied both the Spirit Transformation Technique and Impure World Reincarnation, he had sensed something "abnormal" about the latter.
Among known "reincarnation techniques," Impure World Reincarnation was an outlier.
The Self-Reincarnation Technique Chiyo might one day develop, the Dragon Life Reincarnation passed down in the Land of Grass as a kekkei genkai, the Rinne Rebirth of the Rinnegan… these techniques share two common features: "time sensitivity" and "vessel."
Self-Reincarnation and Dragon Life Reincarnation both require the caster to transfer their entire life force and chakra to revive someone who had died recently.
Rinne Rebirth, while not necessarily fatal to the caster, increased in cost the longer the target had been dead.
That was "time sensitivity."
The need for a "vessel" was similarly straightforward. The first two techniques transferred life force directly to a "corpse" simple resurrection of the dead.
Rinne Rebirth seemed to transcend this limitation, even reviving those summoned by Impure World Reincarnation in their original forms. But as mentioned, Impure World Reincarnation itself was an outlier.
Impure World Reincarnation used the target's genetic information as a medium, pulling the soul into a living "sacrifice" as a vessel, resurrecting them in a zombie-like form.
In common terms: borrowing a corpse to return a soul.
The external form and the consciousness driving the body were not the sacrifice's, but the summoned soul's.
Thus, when Rinne Rebirth revived an Impure World Reincarnation target, the recipient was not the sacrifice's original body, but the physical data of the reincarnated soul layered over it.
Yes physical data.
Impure World Reincarnation even allowed the caster to decide what age the resurrected person would appear as.
As its often-overlooked prefix "Summoning Technique" implies, this technique was not truly "reincarnation," but summoning a soul from the afterlife into a vessel.
But this raised another question: was what Impure World Reincarnation summoned truly a "soul"? Or rather, what was a "soul" in this world?
In Hii Kōri's previous life, there was a famous curse user whose technique was Séance.
Unlike Ino Takuma's technique which turned himself into a medium to summon imaginary phantom beasts that old woman's technique overwrote a medium with the "physical" or "soul" data of a deceased person.
In principle, it wasn't recreating a body or summoning a dead soul. It was downloading a data package and renaming it to match an existing old file, then merging the new "file" with the old one.
Sounded rather similar to Impure World Reincarnation, didn't it?
Though there were examples of souls being sealed, Impure World Reincarnation from working—that was itself a paradox.
In this world, the destination of the soul was somewhat ambiguous. Though the Pure Land existed as a confirmed other dimension, souls could linger in the living world through obsession and will.
In the original story, Sakumo Hatake's soul appeared to his son Kakashi after his death. Obito Uchiha also remained in the living world temporarily, even gifting his Sharingan and power to Kakashi.
Indra and Asura Ōtsutsuki continued their conflict after death, their chakra carrying their will to fight through successive reincarnations.
But the concept of "chakra reincarnation" was already quite absurd.
As everyone knew, chakra was a mixture of physical and spiritual energy. After death, physical energy ceased. Spiritual energy's effect could, at a certain moment, momentarily spike to nearly infinite.
The pendant Hii Kōri carried, or the "Susano'o-mama" in the original story—products of "Post-Mortem Nen"—were born from such phenomena. "Chakra reincarnation," then, was closer to an engraved obsession.
These phenomena all suggest that, freed from the body's constraints, a soul driven by strong will held considerable control over itself.
If judged by summoning principles, summoning a soul from the Pure Land—a different dimension—was far harder than summoning one from a "seal."
Regardless of special cases like the Six Paths tools or the Shinigami, even a soul sealed by ordinary techniques could not be summoned by Impure World Reincarnation.
That seemed illogical.
When practicing the Spirit Transformation Technique, Hii Kōri could feel that even when separated from his body, his soul still maintained a connection to it on another level.
This feeling was different from the soul-state he had experienced in his previous life when taking a "soul-striking" punch from a certain pink-haired classmate.
At first, he hadn't thought much of it perhaps it was just the binding effect. But now he considered: maybe this was the difference in the nature of "souls" between worlds.
In his previous life, the soul was the "essential nature" that existed before the body. The "soul data" summoned by séance was a copy of the soul. In this world, what mattered decisively was "consciousness"—the "self."
Soul and body were not different; both were merely carriers of "personality" and "memory." The Pure Land was not an afterlife, but a massive server that recorded the data of the dead in the form of "souls."
When the body died, the soul dissipated. The data, having lost its container, was absorbed into the Pure Land and reshaped into a soul.
To test this hypothesis, Hii Kōri had performed two Impure World Reincarnations targeting living persons as controls, then a third targeting himself.
Though during his Black Flash he had remodeled his brain through that momentary sense of omnipotence, regaining his technique, and his soul had fully fused with his body through the binding effect, this body was still his original body's remnant.
So if he used his own blood as a medium and set the summoned form to around five years old, what would happen?
The result had confirmed his hypothesis.
"Experiment 3: Using target 'Hii Kōri's' blood as medium, 'Ōtani Makoto' as vessel. Technique activated successfully, but encountered a logical bug at the final stage and failed to fully manifest."
Judging by the body's classification, most of his original body's soul had already dissipated and been recorded in the Pure Land fitting the definition of "deceased." That was why the technique could activate.
But when the corresponding soul data was downloaded into the vessel, the "unique" physical data conflicted, and part of the soul data was duplicated. Under these circumstances, Impure World Reincarnation naturally could not continue.
"Ah… fascinating."
Though all three attempts had technically failed, the conclusions Hii Kōri had drawn from them were a massive gain. Preparing the soil wasn't difficult, and biological materials were easy to find.
He stretched. His spirit-thread nerves cut off the man's ear, then slit his throat.
The gurgling beneath the gag turned into a wet, hissing sound. Blood mixed with filth, smearing the formula beneath him into a mess.
Hii Kōri snapped his fingers. A Scorch Release orb flashed over the man, incinerating his body, the filth, and the formula in one stroke.
Then, the spirit-thread nerves redrew the formula. Rashōmon released another prisoner—similarly stripped, similarly bound and immobile.
"Alright. Let's use you to test whether the vessel's gender affects compatibility with a soul of the opposite sex."
He kneaded the freshly severed ear into the soil. His gaze never lingered on the naked body before him. He used his spirit-thread nerves to restart the tape recorder and cameras, muttering to himself:
"Hmm… but 'testing differences' aside, this version of Impure World Reincarnation has such low precision…"
He glanced at the woman's data, clicked his tongue in mild displeasure, but said nothing more.
After all, Tobirama Senju had originally created Impure World Reincarnation solely to support his Mutual Explosive Tags which would otherwise engulf the caster along with everyone else. Precision hadn't mattered at all.
If he wanted to complain, he'd have to dig up Tobirama's grave, summon the white-haired man, and complain to him directly.
"Ah... Orochimaru... when are you going to defect... I want to do research with you..."
Sighing wistfully, Hii Kōri pressed his hands together once more. Fourth… "Experiment 3: Using target 'Ōtani Makoto's' flesh as material…"
***
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