One year later, in a remote mountain area of the Fuwai District.
This was originally a Sakkise mine, and Katori Nanatsuki had already excavated more than half of it.
He deliberately left some Sakkise in the outer regions, then built a laboratory within the hollowed-out space inside.
Inside the lab, Aizen Sōsuke, Hoshino Rie, and Katori Nanatsuki were each busy with their own tasks.
On the operating table in front of Nanatsuki lay a young boy.
It was a Reishi Shell he had created using artificial body techniques.
However, this shell had not yet been imbued with consciousness—it was essentially a vegetative husk.
After building the lab, Nanatsuki decided to hone his skills in artificial body manipulation.
Aizen Sōsuke had improved rapidly. Under Nanatsuki's guidance, in just one year, his proficiency in Kaido, medical techniques, and spirit body knowledge had already surpassed that of a standard Fourth Division member.
He was now capable of assisting Nanatsuki directly.
Nanatsuki was checking various data related to the Reishi Shell. Since its consciousness hadn't been activated yet, it was merely a mindless Reishi construct—perfectly suitable for experimentation without any psychological burden.
Without turning his head, Nanatsuki asked,
"Sōsuke, is the extraction fluid ready?"
Aizen Sōsuke handed over a test tube filled with white liquid.
"It's ready for use at any time."
Nanatsuki nodded slightly, took the test tube, and inspected the contents.
"Good extraction. Your technique is getting more refined."
Aizen replied humbly,
"All thanks to your devoted guidance, Sensei."
Nanatsuki turned to the busy Hoshino Rie.
"Rie, is the catalyst ready?"
Rie quickly responded,
"Almost…"
A moment later, she handed over a vial of blue reagent.
"Sorry for the delay! I was too slow!"
"No need to rush," Nanatsuki said gently.
"You still work at the Fourth Division. Just helping out already means a lot to me."
He used a syringe to extract the blue reagent and injected it into the test tube containing the white liquid.
After mixing thoroughly, the blue hue disappeared, returning the liquid to a pure white.
Nanatsuki switched syringes and injected the white fluid into the Reishi Shell.
The veins on its arm swelled to two or three times their original size, clearly visible even beneath the skin.
As the white liquid made contact with the blood, it seemed to come alive within the vessels, causing the entire vein to writhe violently beneath the skin.
It was like a tiny white snake had burrowed into the shell's skin, squirming restlessly beneath the surface.
The little white "snake" rapidly expanded and spread through the arm. Some white substance seeped from the blood vessels.
The entire forearm swelled, and the white substance stretched the fingers into elongated claws.
This change spread quickly across the body—the Reishi Shell was undergoing extreme transformation.
Then suddenly, the transformation halted.
The bloated white substance disintegrated and collapsed. Some dissolved into Reishi, dissipating into the air. Others lost their activity and fell lifelessly onto the table.
Moments later, the operating table was a mess.
"As expected, it's not that simple." Nanatsuki wasn't surprised by the results.
What he was attempting was Hollowfication of the Reishi Shell.
The white liquid had been extracted from the pair of Divine Armaments that allowed Shinigami to use Sonído.
His research revealed that the Divine Armaments were made from a unique Hollow body.
By feeding it with Reishi, the Hollow material would grow and divide.
This unique ability had provided the lab with a wealth of experimental materials.
"I've got a few ideas to improve the catalyst. Let's try again next time. Clean up the table and log the experiment—I've got a class at the academy."
With that, Nanatsuki left the lab.
Since establishing it, he'd been able to accept new teaching assignments.
Now that he conducted experiments with students, he could take on experimental teaching missions.
He glanced at the Status Interface:
[Guided Aizen Sōsuke in Reishi Shell Hollowfication Experiment (Completed)]
[Guided Hoshino Rie in Reishi Shell Hollowfication Experiment (Completed)]
Both had observed and learned throughout the entire process, and completing the experiment also completed two teaching tasks.
These experimental teaching missions weren't one-time-only, but each student could only earn a reward once per experiment.
Unlike training missions, they didn't require mastery—just some progress to be rewarded.
The rewards scaled dynamically based on the experiment's complexity and duration.
After final calculation, Nanatsuki received 30,000 General Ability EXP.
He dumped all the EXP into Reiatsu, raising it from level 89 to level 90.
Third-class Spiritual Pressure!
After a year of effort and growth, Nanatsuki's Reiatsu had finally reached the level of a Captain.
His Status Interface had significantly changed:
[Basic Abilities: Reiatsu Lv90, Zanjutsu Lv85, Kidō Lv70, Hakuda Lv60, Shunpo Lv60]
Over the year, his Hakuda had improved too. Now, there were no major weaknesses.
Knock knock.
Nanatsuki had just arrived at his office when someone knocked on the door.
Since becoming Swordsmanship Department Head, he had his own private office.
"Come in." He poured a cup of tea to moisten his throat before class.
It was Danmu Zōsuke.
"Department Head, Kotetsu Ayane is looking for you," he said.
"Is it urgent? I've got class soon," Nanatsuki asked.
"I'm not sure… Dean Kotetsu didn't say. She just asked me to tell you as soon as I saw you," Zōsuke scratched his head. "I can cover your morning class if needed."
"I'll take you up on that. I'll teach your afternoon class in return," Nanatsuki nodded.
He didn't like making his subordinates work overtime for nothing.
"Awesome! I've got a blind date tonight, so I can go prep early!" Zōsuke beamed and left.
Nanatsuki finished his tea and headed to the dean's office.
"Dean Kotetsu, you wanted to see me?"
"The graduation exam missions have been finalized," said Kotetsu Ayane, handing over a document.
"I asked you here to give you an early look."
Kuchiki Sōjun, Ōmaeda Kishinosuke, and Nanatsuki's four disciples had all applied for early graduation.
They'd have to pass the exam to qualify.
The one leading them through it: Katori Nanatsuki.
Nanatsuki picked up the document and reviewed it.
His eyes narrowed slightly.
"The mission site is Hueco Mundo?"
Kotetsu Ayane nodded.
"Early graduation assessments are tougher than normal ones. But both Soul Society and the World of the Living have been quiet lately. There's no more fitting mission than this one."
After last year's Quincy eradication campaign, the remaining Quincy had gone into hiding. There hadn't been any attacks on Shinigami in a long time.
This allowed Soul Reapers stationed in the human world to focus entirely on Hollows, and things had settled down considerably.
"But isn't Hueco Mundo too dangerous?" Nanatsuki frowned. "Even if they've all learned Shikai, they're still students with limited combat experience."
Ayane explained,
"Don't worry. It's just a supply transport mission to support the Hueco Mundo expedition force."
"You won't be participating in the war. Just delivering goods."
"Hueco Mundo is barren, and the expedition force needs a lot of supplies. These missions are common and rarely dangerous."
She pulled out a map.
"This shows the layout of Hueco Mundo. Stay away from marked danger zones. Finish the mission quickly and return safely."
"Thank you, Dean. I'll prepare well to ensure the exam goes smoothly." Nanatsuki nodded, taking the map.
It marked the expedition force, Las Noches, the Forest of Menos, and the Hueco Mundo Desert.
Several danger zones were marked, places where powerful Menos Grande were known to lurk.
"Do you remember Ashido?" Ayane asked with a smile. "He's your contact for the delivery."
"Ashido… It's been a while," Nanatsuki recalled the red-haired man.
They hadn't seen each other since Ashido had gone to Hueco Mundo.
Suddenly, memories from his previous life surged forth—he remembered how Rukia met Ashido alone in the Forest of Menos in the future.
That wasn't right.
Ashido had become the captain of the expedition force. A man like that shouldn't be wandering the forest alone.
'Meeting him there might not be a good sign,' Nanatsuki thought.
To prevent anything unexpected, he decided to prepare thoroughly before heading to Hueco Mundo.
Katori Nanatsuki's laboratory was split into two sections:
One for experiments, the other—sealed off—served as a training ground.
Thanks to the presence of Sakkise, nothing that occurred inside could be detected from the outside.
Nanatsuki took out a pure-white humanoid doll.
This was the Bankai Training Doll he had obtained earlier.
The Bankai Training Doll was a shortcut for training Bankai.
Normally, even if your Reiatsu reached the threshold for Bankai, it still took years—sometimes over a decade—of practice to achieve it.
But the Bankai Training Doll could dramatically shorten that time.
By inserting one's Zanpakutō into the doll, it would manifest into physical form.
The manifested Zanpakutō spirit could remain for three days.
If one could defeat it within those three days, they could obtain Bankai.
Now that Nanatsuki's Reiatsu had reached Captain-class, he finally had the qualifications to undergo Bankai training.
He drew Kagehime and inserted it into the doll.
Kagehime and the white doll slowly disappeared.
A sensation bloomed in his chest, and when he looked down, he saw a clump of shadow silently peeling away from his own shadow.
It rapidly expanded until it blanketed the entire training ground, dyeing everything pitch black.
The shadows on the ground squirmed as if something was flowing inside them, writhing irregularly.
Gradually, the darkness rose into the air, condensing into a long-haired girl clad in black.
"I have entered the real world at last~" Kagehime lifted her dress and spun around, lively and full of spirit.
"Kagehime, I finally get to meet you in reality," Nanatsuki said softly.
"Indeed. It means you've grown quite a lot, Master. But…" Kagehime smiled playfully.
"If you want to unlock more of my power—you'll have to defeat me first~"
"Then can I use Datenshinkotsu?" Nanatsuki asked with a smile.
"Of course not. You can only use these black blades lying on the ground," Kagehime said, drawing one of the black swords embedded in the earth.
Nanatsuki looked around. From the ground dyed in shadow, countless jet-black blades had emerged.
He casually pulled one out and tested its weight.
'Feels like an Asauchi.'
"If that's the case, you won't beat me easily. Just don't tell me you can use my sword techniques too," Nanatsuki said, gripping the hilt between two fingers.
"I'm just a Zanpakutō spirit. What would I know about swordsmanship?" Kagehime rolled her eyes.
"But defeating a shadow won't be so easy, you know~"
Nanatsuki slashed. A beam of Flowlight burst across the black space.
Kagehime, seemingly unguarded, was sliced in half.
But she wasn't an ordinary spirit. Inside her bisected body, there were no organs—only pure shadow.
"Aww, so impatient," she teased, her split body merging back together without a trace of injury.
"Regular attacks don't work on shadows~"
"You'll have to find the one blade in this sea of swords that can defeat me."
"So it's not about power—this is hide-and-seek," Nanatsuki chuckled.
"Exactly~ You've got three days to win this little game of hide-and-seek~"
Kagehime's body vanished—then immediately reappeared behind him.
Nanatsuki raised his arm in time to block her slash.
But her blade, like her body, was made of shadow. Even as he split it in half, the two pieces fused back together and continued their arc toward him.
Shhk!
Nanatsuki couldn't dodge in time—a gash opened on his shoulder.
"Your blade has the same properties… That's going to make this tough," he said seriously.
Her blade regenerated like a shadow, just as she did.
That meant he couldn't block—he could only dodge.
And since she wasn't afraid of being cut, trading blows was out of the question.
Nanatsuki shrugged off his upper robe. Reiatsu surged from his body as turbulent spiritual pressure burst from his shoulders and back.
He activated Shunko, using speed to dance with Kagehime in a deadly tug-of-war.