Invasion
In his base, Orochimaru was engrossed in his research.
Through the White Zetsu's bodies, Orochimaru had made significant breakthroughs in several of his experiments — most notably in improving vessels for reincarnation techniques.
He had been studying Edo Tensei (the Summoning: Impure World Reincarnation) and related methods. According to Orochimaru's research, ordinary Edo Tensei could not always restore a deceased person to their full former strength; the quality of the vessel and the sealwork made a substantial difference. However, when a White Zetsu's body was used as a living vessel, that gap could be dramatically reduced due to the peculiar properties of the tissue.
Orochimaru had also been experimenting with transferring a spirit between bodies as a means to extend life. He believed that to achieve true longevity he needed a method to solve the problem of the aging body.
He reasoned that cellular replication is finite: after many divisions, the rate of cell division slows, aging progresses, and eventually cells cease dividing, causing death. A spirit, however, does not age in the same way a body does. Therefore, Orochimaru conceived of transferring his spirit into another person's body repeatedly — replacing bodies when they failed — to achieve effective immortality.
During his experiments, Orochimaru discovered a key difficulty: when a foreign spirit was placed into another body, the host's cells often accelerated their division in an attempt to accommodate the foreign spirit; they exhausted their replicative capacity and the body then collapsed. This rapid failure did not follow the normal, gradual aging process but instead resulted from accelerated cell turnover that burned through the tissue's limits.
Orochimaru compared spirit and body to sword and scabbard: each soul is unique and each body is unique; the scabbard must be shaped to fit the sword. If a different sword is forced in, the scabbard will try to reshape and may rupture. Likewise, when a soul is suddenly placed into an incompatible body, the body attempts to adapt by accelerating cell division, and when division reaches its limit, the body dies.
He had been working on methods to inhibit or regulate that accelerated cell division — first managing it for days, then weeks, then months — but the farther he pushed the timespan the harder it became to control. Without the White Zetsu tissue, he might still be struggling to extend the usable lifespan of a transplanted spirit.
The White Zetsu material, however, suggested new possibilities. Through testing, Orochimaru found that if his spirit were transferred into a White Zetsu body it could endure far longer — on the order of years rather than weeks — because the Hashirama-derived vitality present in those tissues granted far greater regenerative endurance. The White Zetsu bodies were thus a versatile substrate for experimentation.
Orochimaru already knew that one child among the sixty test subjects in the Hashirama-cell experiments had survived and manifested Wood-like properties: Yamato. That demonstrated the basic viability of infusing Hashirama's cells into a human host and gave credibility to the approach.
If he used White Zetsu tissue as a blueprint and combined genetic modification, cell transplantation, cloning, and other techniques to fashion a body optimized for his spirit, then — in theory — he could create repeatable vessels that would accept his soul and endure for long periods. The first prototypes might be imperfect, but Orochimaru was confident that given time he could refine them toward perfection.
At present, however, Orochimaru had not yet mastered every piece of the process. Some techniques were immature, and he had not yet attempted a full transfer of his own spirit. Therefore he resolved to run a controlled trial of the transfer once — only by experiencing the procedure himself could he discover its shortcomings and iterate improvements.
Of the original White Zetsu specimens he possessed, two remained: one reserved for experimentation, the other prepared as a reincarnation vessel. That was not enough. Orochimaru planned to request additional White Zetsu tissue from Chi Yu later to accelerate the work.
Orochimaru left his laboratory and found a snake waiting at the door. When he appeared, the snake writhed, opened its mouth, and expelled a small ring and a folded scrap of paper. Both were sticky, but Orochimaru did not care; he picked them up.
A single sentence was written on the paper:
[Action will be taken against you tomorrow night. The ring can be used for contact. See you next time, Orochimaru-sensei.]
Orochimaru's lips curved faintly.
He had not yet left Konoha; he had been waiting for Hiruzen Sarutobi to act, and now that day had come. Hiruzen had once been his teacher, and Orochimaru wished that Hiruzen would be the one to end everything — or to let him go. If Hiruzen acted, Orochimaru would see the truth of their bonds. If Hiruzen did nothing, Orochimaru would leave the village and pursue his experiments without pretense.
The reason Orochimaru had not openly used Edo Tensei or attempted full soul transfers in Konoha earlier was to avoid needless trouble and exposure. This moment had finally arrived; he had waited a long time.
He tucked the ring away, burned the note, and began packing the laboratory.
...
The next evening.
Hiruzen Sarutobi stood in the ANBU base already clad in combat attire. Behind him stood five elite ANBU, Kakashi among them. Hiruzen looked up at the night, now dark, and said in a low voice, "Follow me."
Hiruzen led the team toward Orochimaru's compound.
They reached the perimeter a short time later. Just as Hiruzen was about to move in, Kakashi stopped him. "Please wait, Third Hokage. Orochimaru has set a barrier around the base. If it's triggered, he'll be alerted. I've seen Chi Yu release one like this before, so I know how to disable it."
Hiruzen nodded. "Good. Kakashi, disable the barrier."
Kakashi, confident that Chi Yu had likely warned Orochimaru, moved quickly — eager to demonstrate his skill and earn Hiruzen's trust. He performed the hand seals with practiced speed and pressed his palm to the ground. A faint sealing sigil appeared beneath his hand, the barrier's mark, and with another set of seals he called, "Release!"
The wards around Orochimaru's base collapsed.
Hiruzen and his team entered the compound, and under Kakashi's guidance they reached the door of the laboratory room where sealing techniques had been applied. Sounds came from within; Hiruzen judged Orochimaru was mid-experiment.
Hiruzen forced the sealing glyph aside, threw the door open, and led his team in.
Orochimaru turned to look at Hiruzen. His expression was calm; a smile curved his lips, but there was no warmth in it.
"Hiruzen-sensei," he said softly, "have you come to kill me?"
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