Chapter 90: The Stabilizer

After Tsunade and Kakuzu left, Ren remained at his desk and reopened the Medical & Ocular Care category.

The blue interface returned to the three products he had examined the previous evening. His current balance appeared at the top of the screen.

[Current Business Capital: 629,200 BC]

He had already decided his priority. He bypassed the Commercial Seal Press and the Spatial Anchor Tags, leaving them unpurchased, and opened the full listing for the Ocular Stabilization Formula.

The initial listing had shown a price of 120,000 BC. Opening the complete purchase window revealed an additional requirement.

[PERSONALIZED CATALYST REQUIRED.]

The standard formula could repair damaged ocular pathways, but Ren’s right eye already contained treated Hashirama cells from Tsunade’s work. To prevent the medicine from disturbing those cells, the System required a catalyst prepared specifically for his eye.

The System offered the complete package:

[Ocular Stabilization Formula — 120,000 BC]

[Personalized Ocular Reconstruction Catalyst — 80,000 BC]

[Total Cost — 200,000 BC]

Ren stared at the total.

Two hundred thousand BC.

At the System’s ten-to-one conversion rate, the treatment represented two million ryo in clean profit. Ren had spent more money on larger projects, but very few purchases had swallowed that much BC at once.

"For this price," Ren muttered to the empty room, "the medicine should repair the eye, improve my vision, and personally apologize for the inconvenience."

He closed the other shop listings. His eye came first.

He confirmed the purchase.

[200,000 BC DEDUCTED.]

[REMAINING BUSINESS CAPITAL: 429,200 BC]

A sealed medical case appeared on the desk.

Inside, resting in dense foam, were two vials. One contained the clear base stabilization formula, and the other held the personalized catalyst. Beside them rested a thick sheet of preparation ratios and strict instructions.

He read the parchment carefully rather than touching either vial. The two substances had to remain separated until immediately before treatment. Once mixed, the medicine had to be used within several hours.

Ren closed the case. Tsunade would have to do this tomorrow.

The next morning, Ren arrived at Konoha General Hospital carrying the sealed case.

He found Tsunade already inside her private laboratory. She was standing over a stainless steel table, examining several prepared tissue samples under a medical lens. One tray contained the preliminary medicine she had successfully developed after his last experimental treatment.

Tsunade looked up when the door closed behind him.

"Good. You’re here." She set aside the notes she had been reading. "I was going to send someone to find you."

Ren set the medical case on the edge of the table, leaving the latch closed. "Why?"

"The preliminary medicine is ready," she explained, gesturing to the tray. "The recovered binding compound remained stable when I mixed it with your blood, and the treated Hashirama cells are no longer spreading into the surrounding tissue. The first treatment is still holding."

She picked up a prepared dropper. "The next step is testing a stronger dose directly on the damaged eye."

Ren examined the prepared dropper. "You want to test another experimental dose directly on the eye?"

Tsunade continued adjusting the medical lens. "It is called treatment."

"Treatment usually involves medicine that has already been proven to work."

She finally looked up at him. The formula had been synthesized from Ren’s blood and tissue and designed specifically for his damaged eye. Testing it on another patient would tell them nothing.

Ren glanced back at the dropper. "That is a very professional explanation for why I am the only available guinea pig."

Tsunade returned her attention to the sample. "Stop complaining. Unless we test it, we have no way of knowing whether the research is moving in the right direction."

Ren reached out and slid the System medical case across the table, stopping it right beside her experimental tray.

"Put the preliminary dose aside," Ren said. "I already found the finished treatment."

Tsunade paused. Her gaze moved from the unmarked case to Ren’s face before returning to the case.

"Please tell me you didn’t buy medicine from the first underground merchant who promised to fix a Sharingan."

Ren rested one hand on the lid. "He was at least the third."

Tsunade’s expression hardened.

"That was a joke," Ren added.

"How much did you pay for this?"

"Two million ryo." Ren rested one hand on the lid. "At that price, I expected a new eye rather than a bottle of medicine."

Tsunade flipped the latch and opened the case. She examined the two sealed vials and the detailed preparation instructions. The professional packaging didn’t impress her.

"Where did you obtain it?" Tsunade demanded. "Did the seller know the eye was a Mangekyō Sharingan? Did they know Hashirama-cell material had already been introduced, or that the chakra pathways were physically shattered? Did they know my initial binding compound was still active?"

"The treatment was prepared specifically for my condition," Ren told her.

Tsunade looked at him much more closely. "And you trusted this supplier enough to spend two million ryo without seeing a single clinical test?"

"The supplier has never delivered a defective product," Ren said. "But I still brought it to the best medical ninja in Konoha instead of opening the case and pouring it into my eye."

Some of the suspicion left Tsunade’s expression, although her hand remained firmly planted on the medical case.

"Administer it," Ren said.

Tsunade immediately snapped the case shut. "Absolutely not. Confidence in a supplier is not a medical test. Nothing enters your eye until I know exactly what it does when exposed to your tissue and chakra."

Ren pointed toward the preparation sheet. "The instructions already explain the reaction."

"Whoever wrote those instructions will not be standing here if your optic nerve dissolves." Tsunade dragged the case fully onto her side of the table and reached for a clean syringe. "Roll up your sleeve. I need another blood sample."

Tsunade took another small blood sample and added it to material left from the previous evening’s treatment. She divided the mixture between two clean glass dishes.

The first received a drop of her preliminary medicine. As before, the treated Hashirama cells stopped spreading. When Tsunade increased the chakra flowing through the dish, thin cracks began appearing around the damaged tissue.

Her mouth tightened. "It can keep the cells contained, but the pathway still can’t endure Mangekyō chakra."

She opened the System case and carefully mixed a small test amount of the stabilization formula with the personalized catalyst. The instructions required only a few drops, leaving the main vials untouched for the actual treatment.

Tsunade applied the mixture to the second dish.

The damaged tissue drew together. The treated cells settled around it without spreading, and when Tsunade increased the chakra pressure, the repair held.

She pushed more chakra into the sample.

It continued holding.

Ren watched her repeat the test twice before asking, "Was I scammed?"

"Stop looking pleased." Tsunade leaned closer to the dish and examined the repaired section again. "The medicine is genuine. I’m still testing it before it goes anywhere near your eye."

Tsunade refused to let Ren leave while the testing continued. She might need another blood sample, and once the two medicines were mixed, the treatment would have to begin before the formula became unusable.

Ren spent the next several hours in the corner of her laboratory, eating a bland hospital lunch while she worked at the counter.

Ren pushed the tray away. "This food is worse than the medicine’s price."

"Hospital food is designed to keep patients alive," Tsunade said, charting another successful reaction. "Not happy."

"That distinction explains several things about your personality," Ren replied.

Tsunade paused. She briefly considered throwing the metal tray at his head, then decided the sterile environment was more important and went back to her notes.

A hospital assistant entered with clean equipment and carried away the used glass trays. Ren opened his mouth to ask for salt, but the woman had already closed the door behind her.

During the waiting period, Tsunade examined Ren’s eye directly. The grey clouding hadn’t worsened, but the fractured pathways remained far too fragile to risk an activation.

By late afternoon, the final complete-treatment sample had remained perfectly stable under heavy chakra pressure.

Tsunade finally closed her laboratory ledger.

"I can’t find a reason not to use it," she admitted.

Ren put down one of the estate reports he had brought with him to pass the time. "That sounds almost like approval."

"It means the medicine passed my tests," Tsunade corrected sharply. "Approval depends on whether it actually works inside the eye."

Ren stood and moved to the treatment chair.

Tsunade prepared the two medicines, drawing them into a sterile dropper using the exact ratio required. The moment the base formula mixed with the personalized catalyst, the clear liquid changed into a faint, glowing silver-blue.

She pressed a specialized chakra-monitoring seal against Ren’s right temple, ensuring it adhered securely to the skin, and checked his pulse.

"How painful is this going to be?" Ren asked.

Tsunade looked at him, answering completely honestly. "I don’t know."

"This is precisely why I objected to being a guinea pig."

"You can leave with one damaged eye and two unopened vials whenever you want," Tsunade offered, holding the dropper steady.

Ren didn’t move. He leaned his head back against the leather rest and opened his right eye.

Tsunade administered the medicine.

The pain arrived immediately.

It didn’t build. It hit as a sharp, vicious burn straight across the surface of the eye, before driving deeper along the damaged optic pathways.

Ren’s hand closed around the metal arm of the chair. His knuckles went white, but he remained absolutely still. Moving now could ruin the delicate binding process.

The marks across the monitoring seal jumped sharply as the medicine reached the damaged sections. Tsunade placed two glowing fingers against Ren’s temple, following the reaction with her medical chakra.

The treated cells gathered around the fractured pathways without spreading farther into the eye. For several tense seconds, the marks on the seal continued shifting. Then the fluctuations weakened and settled into a steady pattern.

The burning pain lasted for less than a minute.

It ended suddenly, replaced by a strange, numbing cold sensation moving slowly behind the eye.

Then, the constant, dull ache that had followed Ren for weeks simply disappeared.

Ren kept his right eye closed. He waited, his breathing slow and measured, until Tsunade finished examining the chakra pathways with her medical ninjutsu.

She peeled the monitoring seal off his temple.

"Open it," she instructed.

Ren opened his eye.

The grey film was gone. The bright, sterile examination light above the chair was painfully harsh for the first few seconds, making him squint. But as his pupil contracted, his vision rapidly adjusted.

The room returned in sharp detail. He could see the fingerprints Tsunade had left on the glass vial and read the small serial numbers stamped onto a cabinet across the laboratory.

Ren turned toward the smallest writing chart on the opposite wall and read the bottom line aloud without hesitation.

Tsunade leaned in with a penlight, checking his pupil dilation one last time.

"The ordinary vision has returned completely," she confirmed, stepping back.

"Does that mean the Mangekyō ban is over?" Ren asked.

"We still need to confirm that the repaired pathways can safely handle the chakra—"

Ren didn’t wait for her to finish the sentence. He gathered his chakra and pushed it directly into his right eye.

The crimson iris flared to life. Three black tomoe appeared instantly.

Tsunade started to object, raising a hand, but the tomoe were already stretching and shifting, locking into the sharp, intricate pattern of his Mangekyō Sharingan.

Ren braced himself.

There was no tearing pain.

There was no blood leaking down his cheek.

The Mangekyō pattern settled into place while his vision remained completely clear.

Ren waited for the familiar, agonizing pain to follow.

It never came.

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