After parting ways with Itadori Yuji, Kamo Itsuki immediately returned to his research base and dedicated himself wholeheartedly to studying Itadori Yuji's blood.
After a period of diligent research, Kamo Itsuki finally completely understood Itadori Yuji's condition.
Itadori Yuji was a vessel meticulously prepared by Kenjaku for Sukuna, yet it was vastly different from ordinary vessels.
According to Kamo Itsuki's research findings, one of sukuna's fingers had been mixed into Itadori Yuji's body.
Coupled with the fact that Itadori Yuji's father was the reincarnation of Sukuna's twin brother, and Kenjaku's in-depth research into the cursed womb: Death Paintings, these conditions ultimately created Itadori Yuji, a vessel capable of containing Sukuna's immense Cursed Energy.
Kamo Itsuki currently did not possess the conditions that Kenjaku had back then; it would be almost impossible for him to recreate an Itadori Yuji from scratch.
However, he also had no such need.
Kamo Itsuki was not trying to create a vessel for Sukuna, but rather a "sukuna's finger Detector."
Now with Itadori Yuji's blood sample and his current technological accumulation, Kamo Itsuki felt that it wouldn't be a big problem.
Kamo Itsuki now controlled six of sukuna's fingers, and counting Itadori Yuji, it could barely be considered seven.
With these seven fingers, even if all the other fingers were acquired by Kenjaku and used to revive Sukuna, it wouldn't cause much trouble.
Sukuna with the strength of thirteen fingers would only be slightly stronger than a Special Grade Cursed Spirit, so there was no need to fear him.
However, Kamo Itsuki still planned to collect as many of sukuna's fingers as possible.
This was not for precautionary measures, but for Sukuna's vast Cursed Energy.
Years ago, Kamo Itsuki had already planned to set up a super barrier that would cover all of Japan.
Now, the preliminary design for the Barrier was basically complete.
However, there was still one major problem that needed to be solved: the power source.
To maintain such a massive Barrier in normal operation, a huge amount of Cursed Energy would be required.
According to Kamo Itsuki's current design blueprint, at least the amount of Cursed Energy equivalent to twenty Special Grade Jujutsu Sorcerers would barely be enough.
However, the Jujutsu World currently only had four Special Grade Jujutsu Sorcerers, and all the other ordinary Sorcerers combined would not reach the amount of twenty.
Moreover, to get all Sorcerers to unite and hand over their Cursed Energy to Kamo Itsuki for use?
The thought alone seemed impossible, unless some great disaster that threatened the entire Jujutsu World occurred.
Therefore, Kamo Itsuki had to find a way to fill this gap himself.
Kamo Itsuki had also considered using his own Cursed Energy to operate the Barrier, but that would greatly limit his own strength.
He wasn't so great as to put himself in danger for the sake of the Jujutsu World.
Each of sukuna's fingers possessed Cursed Energy equivalent to that of a Special Grade Jujutsu Sorcerer; the more he collected, the more sufficient the Cursed Energy Kamo Itsuki would have to run the super barrier.
Three months later, inside Kamo Itsuki's research base.
Kamo Itsuki was staring intently at an insect egg on the experimental table.
Several months of meticulous research and cultivation were about to yield results.
This cocoon resembled a black pebble buried deep in a riverbed, with subtle and unique patterns on its surface, emitting a faint, dark luster.
Kamo Itsuki stood with his arms crossed, his expression tense yet full of anticipation.
Suddenly, the cocoon trembled slightly, as if a powerful force was surging within it.
Immediately after, a tiny crack appeared on the surface of the cocoon and gradually spread.
Kamo Itsuki unconsciously leaned closer, his breathing quickening.
With a soft 'crack', the cocoon completely broke open, and a black butterfly struggled to emerge from it.
Its wings were damp, and faint purple patterns adorned its black surface, like mysterious nebulae in the night sky.
The butterfly struggled to break free from the remaining restraints, and Kamo Itsuki held his breath, watching the scene without blinking.
Finally, the butterfly completely detached from the cocoon, and it gently flapped its wings, which gradually became dry and tough.
A relieved and satisfied smile appeared on Kamo Itsuki's face; his "sukuna's finger Detector" was complete, and Kamo Itsuki named it: Yin-Yang Butterfly.
The Yin-Yang Butterfly had only one purpose: it would be attracted by Sukuna's aura.
As long as sukuna's finger existed within a twenty-kilometer radius, the Yin-Yang Butterfly would slowly fly towards it, then land on the target, and transmit the location information to its master, Kamo Itsuki.
Moreover, the Yin-Yang Butterfly was a life form that existed between the ethereal and the tangible; it would only become corporeal when it came into contact with its master, Kamo Itsuki, or the target, sukuna's finger.
No other entity could perceive or interact with the Yin-Yang Butterfly in its natural state. It was a ghost in the machine of reality, unaffected by physical barriers, seals, or spatial distortions. A Sukuna finger encased in lead, buried a mile deep, or hidden within a sophisticated barrier would still sing its siren song to the butterfly's unique senses.
Despite its formidable detection capabilities, searching all of Japan with a single entity was impractical. Thus, Kamo engineered a second function: Ambient Energy Replication.
The Yin-Yang Butterfly could passively absorb the diffuse, negative cursed energy that perpetually leaked into the environment from human suffering. It would use this energy to self-replicate, slowly building a swarm. This swarm would then disperse, a silent, invisible net cast over the islands, systematically sweeping for their target.
The trade-off was time. Kamo estimated a minimum of three years for the swarm to reach critical mass and complete a thorough survey. It was a glacial pace, but the hunt for the fingers was a long-term stratagem, not a sprint. He could afford the wait.
He had considered supercharging the replication with his own immense cursed energy, but tests revealed a flaw: excessive input of his personal energy signature would "drown out" the butterfly's delicate attunement to Sukuna's unique resonance. It was a limitation baked into the rules of cursed energy interaction—a form of metaphysical interference—forcing him to rely on the slow, ambient method.
With the primary detector deployed and set on its autonomous course, Kamo's immediate hands-on involvement in the search was over.
'A relief,' he thought, but then a practical consideration surfaced. 'The butterfly finds them. But someone still has to go and retrieve them. Sending puppets for collection would be far more efficient than personally teleporting to every remote location.'
"I suppose the puppet project isn't obsolete after all," he mused aloud, a spark of renewed purpose in his eyes. "The butterfly pinpoints. The puppets procure. I orchestrate. A far more elegant division of labor."
The idea solidified. He would create a small cadre of intelligent, mobile retrieval units—puppets or perhaps a new form of semi-autonomous cursed corpse—tasked specifically with securing the fingers once located. They would be his hands across the map.
Without further delay, Kamo Itsuki turned and walked back into the heart of his laboratory. The schematics for his next creations began to take shape in his mind, a blend of refined puppet jutsu, barrier-derived autonomy, and the ruthless efficiency he demanded. The symphony of his plans required many instruments; he was now forging the next set.