(T/N: Third Chapter!)
Inside Nanatsuki's lab, the cultivation of Saitō Rei's Reishi Shell was accelerating.
"Sensei, Saitō Rei's No. 1 Reishi Shell is undergoing Hollowification distortion," Aizen Sōsuke frowned as he observed the shell's hand morphing.
Bulging white masses of flesh had formed on the shell's hand, coalescing rapidly and enlarging the entire palm.
"What about the other shells?"
"Numbers 1, 2, 5, and 6 have all shown signs of Hollowification."
"Numbers 3 and 4 were grown using the low-dosage, high-frequency method. So far, no signs of Hollowification."
"Good thing I prepared two separate plans just to be safe..." Nanatsuki sighed in relief, silently thankful for his foresight.
After finalizing Saitō Rei's treatment plan, Nanatsuki had opted to produce multiple Reishi Shells just in case. And now, that precaution was proving its worth.
He had divided the shells into groups and used different maturation protocols. The results varied accordingly.
The accelerated method made the spiritual bodies of the shells extremely unstable, and most had undergone Hollowification.
"Shell No. 3 has shown the fastest Reiatsu growth—it's already reached Level 10 Spirit Power. Shell No. 4 is only at about Level 20," Aizen Sōsuke reported while recording the readings from the life-support capsule.
"Level 10... it should barely be enough to sustain Saitō Rei's spiritual body. But her combat strength likely won't return to what it was before her Spiritual Pressure Core was damaged," he added.
Before her injury, Saitō Rei had held a high-ranking seat with Level 6 Spirit Power—an elite among Shinigami.
It was only after her injury that her power had plummeted.
Shell No. 3's Reiatsu, while still far from her original level, now had a Spiritual Pressure Core stable enough to support her spiritual body.
Still, it was clear that even after the replacement, Saitō Rei wouldn't regain her previous strength.
"Time is tight. If we can just keep her alive, that's good enough," Nanatsuki said. "Besides, she was already weakened after the injury—this new Spiritual Pressure Core should at least be an improvement."
"So you're going ahead with transplanting Shell No. 3's core into her now?" Aizen Sōsuke asked, though he sounded a bit regretful.
He wasn't particularly concerned with Saitō Rei's life. What truly interested him was pushing Shell No. 3 to its absolute limits—he wanted to see how far it could be pushed.
Years of experimentation had already proven one fact:
Even Reishi Shells grown from the same origin could differ in constitution.
And Shell No. 3 was promising—Aizen suspected it might even match Saitō Rei's original potential.
"But her condition could deteriorate at any moment. Waiting could make things worse," Nanatsuki said softly. "Besides, pushing Shell No. 3 further might just cause Hollowification. It's better to proceed now."
"Then I'll halt its treatment immediately," Aizen nodded.
Despite his disappointment, he wouldn't oppose his teacher's decision—the lab ultimately followed Nanatsuki's lead.
Nanatsuki used the Denreishinki to notify Saitō Akane to prepare. The transplant couldn't be done in the lab—he had no intention of exposing this place.
Nor could they perform it at the 3rd Division barracks. After all, creating Reishi Shells was forbidden by Central 46—it had to be done in secret.
So the operation was set to take place at the Saitō household.
Soon after, Nanatsuki arrived at the Saitō residence carrying the surgical instruments and Shell No. 3.
Hoshino Rie had already been looking after Saitō Rei here, allowing Nanatsuki to monitor her condition in real time.
Since the procedure was complicated, it was hard to handle alone. Hoshino's presence would also help assist the operation.
"How's her condition?" Nanatsuki asked.
"The high-dose anesthetic has taken effect. She fainted earlier this morning, but recovered shortly after. I believe the damage to her Spiritual Pressure Core caused her Reiatsu to fail at sustaining basic activity," Hoshino Rie replied.
"Then let's begin at once," Nanatsuki nodded.
He was all too familiar with the sudden fainting episodes—Katori Batsu'unsai used to experience them regularly years ago. But ever since he started reinforcing her Reiatsu, they hadn't recurred.
Nanatsuki and Hoshino entered Saitō Rei's room and began setting up the surgical space.
Operating on a spiritual body was far less cumbersome than on a human one. With Reiatsu, Shinigami could achieve feats far beyond mortal medicine.
Nanatsuki didn't even need a scanner to locate the Spiritual Pressure Core.
Picking up the surgical blade, he made a precise incision—the blade easily passed through the shell's skin, cutting open both muscle and flesh.
But he didn't touch the shell's core yet. First, he looked over to Saitō Rei's condition.
The Spiritual Pressure Core was the heart of a Shinigami's Reiatsu, connected directly to the Saketsu and Hakusui.
These two spiritual nodes were critical—they generated spiritual power and were the core of a Shinigami's spiritual body.
Cutting the connection between the core, Saketsu, and Hakusui would result in immediate spiritual death.
On the adjacent table, Hoshino had already exposed Saitō Rei's core, creating a clean surgical window.
"I'm ready here," she said.
Nanatsuki nodded and gently severed the shell's core from its Saketsu and Hakusui.
He then used tweezers to extract the Spiritual Pressure Core from the shell and placed it in a tray nearby.
The core transplant had to happen quickly.
Nanatsuki turned to Saitō Rei and instructed, "Hand me the shell's core once I sever hers. Be ready."
"Understood," Hoshino said as she picked up the tray holding the core.
Once she was in position, Nanatsuki made his cut—detaching Saitō Rei's damaged core from its connections.
Hoshino immediately passed over the replacement.
Nanatsuki, with swift precision, used Kaidō to reconnect the new Spiritual Pressure Core to Saitō Rei's Saketsu and Hakusui.
Only then did he remove the damaged core from her body.
He adjusted the new core's position using the tweezers, settling it precisely into place.
Once secured, he continued applying Kaidō, stimulating the Spiritual Pressure Core and the two spiritual nodes.
Hoshino watched nervously. She knew this was the most critical moment of the entire operation.