Konoha Hospital, top-floor Isolation Zone.
The air felt heavy enough to wring water from it. Inside the specially equipped room, Uchiha Itachi lay on a treatment table surrounded by sealing formulas, as though bound by invisible shackles. The purplish-black corruption on his left chest writhed slowly but stubbornly beneath the suppression of Tsunade's immense medical chakra, like something alive, trying to spread into the healthier tissue around it.
The markings of the Strength of a Hundred Technique on Tsunade's forehead shone with a gentle yet powerful light. Her entire focus was absorbed in the tug-of-war against this dark force. It was neither a conventional toxin nor an injury, but a form of corruption closer to the realm of a "concept," filled with chaos, hunger, and malice toward life itself. Every time her chakra tried to repair the damaged tissue, the dark force retaliated wildly and assimilated it. Progress was agonizingly slow, like trudging through a swamp.
"It's no good... Conventional cell regeneration and toxin neutralization are completely ineffective." Tsunade's brows knitted tightly, her voice heavy with suppressed exhaustion. "This force is constantly consuming his life force to sustain itself, and... it seems to be adapting to the properties of my chakra!"
She could feel that the dark corruption was no inert substance. It was learning, evolving, trying to find weaknesses in her medical chakra.
"Shizune! Prepare Katsuyu's reverse summoning! I need her senjutsu chakra to assist me!" Tsunade made the decision immediately. Her strength alone could only slow it down, not eradicate it. She needed the power of the Katsuyu Sage, whose affinity with natural energy was exceptionally high.
"Yes!" Shizune immediately formed hand seals.
A moment later, a puff of white smoke appeared, and a small, delicate blue slug with a translucent body materialized on Tsunade's shoulder. She was