When Yanagawa and Isshin Shiba stepped inside the Research and Development Bureau, the wide corridors were flanked not by traditional barracks rooms, but by individual laboratories sealed off with high-strength transparent materials and specialized force fields.
The staff inside wore matching white lab coats and were equipped with all sorts of bizarre auxiliary gear, from strange goggles to peculiar masks.
Some stood before consoles performing complex calculations on floating reishi models;
others recorded data from grotesque biological specimens suspended in culture tanks;
and a few were even conducting physical collision experiments that looked downright hazardous.
It was noisy, frantic, and chaotic, yet permeated by a morbid efficiency and fanaticism.
The usual discipline found among the other Gotei 13 divisions was nowhere to be seen, replaced instead by an obsessive pursuit of knowledge and an unyielding desire to probe the unknown.
Researchers clutching clipboards scrawled with mad equations occasionally scurried past, completely oblivious to Yanagawa and Isshin’s arrival, utterly absorbed in worlds of their own.
“Tch.
Every time I come here, it feels like I’ve walked into a completely different realm,” Isshin grumbled, pinching his nose to dodge a puff of purple smoke billowing from a nearby vent.
After stating their business, they were guided into the deeper recesses of the Bureau by a vacant-eyed researcher.
The laboratories here were on a much grander scale, with correspondingly tighter security measures.
Eventually, they arrived before an enormous metal door styled with grotesque extravagance.
The door slid open, revealing an expansive chamber within.
It was packed with countless instruments, test tubes, incubation vats, mechanical wreckage, biological specimens, and monitor screens covered in manic data.
In the center of the room stood a particularly conspicuous cylindrical glass vat filled with an unidentified green liquid, inside of which some bizarre object seemed to be preserved.
The sound of gurgling bubbles echoed through the thick air.
The master of this domain, Squad 12 Captain Mayuri Kurotsuchi, stood with his back to them before a massive console.
His hands danced across countless buttons, levers, and floating holographic screens at speeds imperceptible to the naked eye, a high-pitched, manic chuckle escaping his lips.
“…Yes, just like that!
Show me where your limits lie, my dear Test Subject No.
247!”
He yanked down a heavy lever.
The green vat in the center of the room warped and expanded violently, web-like fractures instantly spreading across its glass!
“Captain!
Spiritual pressure overload!
It’s going to burst!” an assistant wearing a blast mask warned in a shrill, frantic voice.
“Burst?
No!
This is evolution!” Mayuri cackled madly.
Far from aborting the process, he slammed his hand down on another red button.
*BOOM!*
Unable to withstand the strain, the vat violently exploded!
Viscous green fluid and a tempest of wild spirit particles sprayed everywhere, only to be completely deflected by a barrier of reishi that snapped up in front of the console.
When the smoke cleared, all that remained in its place was a tiny pinch of charred dust.
“Tch.
Another failure.
Its tolerance is still insufficient.
Next time, I’ll try introducing some Gillian-class spirit particles…”
Unfazed, Mayuri stroked his chin, the eyes behind his mask gleaming with even greater fervor.
Only then did he seem to notice the two figures standing at the doorway.
He turned around slowly, his gaze sweeping over like a scanner before locking squarely onto Yanagawa.
“Oho?” he breathed.
“A rare guest.
A rare guest indeed.” Mayuri’s voice was sharp and slick.
Spreading his arms in an exaggerated gesture of welcome, the posture felt more like a predator flaunting its lair.
“Lord Yanagawa of Squad 0, and…
Captain Shiba of Squad 10.
Whatever wind could have blown the two of you into my humble laboratory?
“Could it be you’re interested in the failed experiment just now?
It may have failed, but the data is delightfully valuable!
Care to take a look?”
He spoke at a blistering, erratic pace.
“Captain Kurotsuchi,” Yanagawa said, ignoring the man’s bizarre demeanor and cutting straight to the point.
“Pardon the intrusion.
We have come in hopes that the Research and Development Bureau can assist in manufacturing a specific device to aid our investigation into the Twin Hyōrinmaru incident.”
“Oh?
A specific device?” Mayuri’s curiosity was palpably piqued as he sauntered closer.
“Do tell.
Could it be…
you wish for me to duplicate a Hyōrinmaru?
While challenging, it is hardly impossible, you know!
“So long as I have sufficient reishi samples and the foundational forging data from that esteemed ‘God of the Sword’…”
“It’s not about replicating a Zanpakuto,” Yanagawa cut off his dangerous tangent.
“I need a Tenshintai.”
The moment the word *Tenshintai* left his lips, the air in the chamber seemed to freeze.
Mayuri’s movements halted.
The gaze behind his mask turned razor-sharp.
Straightening his posture, he let out a drawn-out, cryptic hum: “Hm—m?”
“The Tenshintai…
one of the little playthings left behind by that fellow Kisuke Urahara.”
Mayuri’s voice remained shrill, yet an indefinable layer of complex emotion crept into it.
“A toy designed to drag a Zanpakuto’s tedious true form into the physical world to play house.
What, could Lord Yanagawa actually be interested in the antique relics Urahara discarded?”
He did not immediately accept or decline.
Instead, he slowly circled Yanagawa, inspecting him like a rare specimen.
“Fabricating a Tenshintai is hardly a difficult feat for me.
“The research materials Kisuke Urahara left behind were a chaotic mess—riddled with personally distasteful ciphers and records devoid of all aesthetic grace.
“However, the core principles and technical details have long since been cracked, optimized, and in certain respects…
completely surpassed by me.”
His tone laid bare his contempt for Urahara’s methodologies, saturated with a borderline obsessive pride and arrogance.
“However,” Mayuri’s tone shifted as he stopped in front of Yanagawa, his eyes boring into him from behind the mask.
“Why should I make it for you?
The status of Squad 0 alone is hardly enough to compel me—Mayuri Kurotsuchi, Captain of Squad 12 and Director of the Research and Development Bureau—to stoop to replicating a primitive toy with limited utility left by a predecessor I have already surpassed.
Unless…”
He extended a long, slender finger.
“…Unless you offer something that interests me in exchange.
For example, cooperating with me in a few specialized research projects?
“Or perhaps…
revealing the *true reason* behind how you earned the favor of Squad 0?”
His demands were blunt, avaricious, and openly probing.
He clearly harbored an immense scientific interest in Yanagawa himself, as well as Squad 0.
Yanagawa turned his head, looking over at Isshin Shiba, who was nervously looking around, distinctly unsettled by the laboratory’s sinister ambiance.
A brilliant idea suddenly struck Yanagawa.
“Captain Isshin,” Yanagawa began, his tone grave and heavy.
“Eh?
What is it, Yanagawa?” Isshin responded instinctively, an ominous premonition prickling his spine.
Yanagawa let out a sigh, as if steeling himself through an agonizing decision.
“As things stand, to obtain the Tenshintai as quickly as possible, uncover the truth, and rescue your future subordinate Tōshirō Hitsugaya…
I’m afraid we have no choice but to ask you to make a small sacrifice.”
“Ask *me* to make a sacrifice?
What do you mean?” Isshin blinked, entirely bewildered.
Yanagawa gestured toward Mayuri, who was watching them with rapt amusement, and spoke with solemn remorse:
“Captain Kurotsuchi’s assistance in producing the Tenshintai requires manpower and resources.
In exchange, he requires a ‘volunteer.’
“Someone to cooperate with the Research and Development Bureau for some…
well, specialized research.
“Captain Isshin, as the Captain of Squad 10, boasting immense spiritual pressure, vast experience, and being Hitsugaya’s prospective superior, by all rights and reasons, this burden can fall to none other than you.”
*Cooperate with research?
In the Research and Development Bureau?
As a “volunteer” for Mayuri Kurotsuchi?!*
Isshin’s eyes bulged as if he had just heard the most horrifying joke in existence.
Unbidden, nightmarish visions flooded his mind: himself strapped helpless to an operating table, surrounded by gleaming surgical scalpels and bubbling jars of unidentified fluid, while Mayuri Kurotsuchi approached with cackling glee, gloved hands dripping with slime as he wielded a syringe the size of a cannon…
*Hiss—!* Isshin sucked in a sharp breath, a cold sweat instantly drenching his back.
He leaped a full pace away from Yanagawa, pointing an accusatory finger right at his nose, his voice cracking:
“Hey!
Yanagawa!
You little brat!
You can’t just throw your teammates under the bus like that!
Selling me out to Mayuri for experiments?!
No!
Absolutely not!
Over my dead body!”
He flailed his arms dramatically, his expression a wild storm of terror, fury, and betrayed disbelief.
He unleashed a barrage of complaints at Yanagawa, completely discarding any sense of decorum, blind to how Mayuri’s eyes gleamed brighter with every second.
Yanagawa remained stone-faced, merely looking at Isshin with an expression that said *this is for the greater good*, as if silently proclaiming: *A necessary sacrifice.*
Isshin cursed and sputtered for several moments, but seeing Yanagawa entirely unmoved while Mayuri appeared genuinely intrigued by the proposal, his heart sank into an icy abyss.
He looked at Yanagawa’s infuriatingly righteous face, and then thought of Tōshirō Hitsugaya, locked away in Central 46 with an uncertain future—the brilliant prodigy he had taken such a liking to, for whom he had already quietly drafted an enlistment form…
A swell of hot-blooded valor mingled with tragic resignation rose within his chest.
Gritting his teeth, Isshin clawed at his hair in agonized inner turmoil, letting out a pained groan.
“Damn it, Yanagawa, you ruthless bastard…
You win!”
Squeezing the words through clenched teeth as if expending every ounce of his remaining strength, his face took on the tragic dignity of a martyr marching to the executioner’s block.
“For Lil’ Shiro’s sake…
I’ll take the fall!
It’s just a little research, right?!
Come on, then!
Captain Kurotsuchi!
Hit me with whatever you’ve got!
If I flinch even once, my name isn’t Isshin Shiba!”
He threw out his chest and squeezed his eyes shut, striking the pose of a heroic martyr ready for whatever slaughter awaited him—though his twitching eyelids and trembling fists betrayed the sheer terror within.
Yet, the anticipated cackle and chilling scalpel never arrived.
Instead, what broke the silence was an unvarnished snort of pure disdain.
“*Pfft.*”
Isshin cracked one eye open in confusion.
Mayuri was waving a bizarrely gloved hand in front of him with blatant disgust, his voice dripping with condescension.
“Isshin Shiba?
Cooperating with research?
*You?*”
He looked Isshin up and down, his gaze as dismissive as if he were appraising an ordinary pebble.
“A thoroughly mediocre captain, an unremarkable Zanpakuto ability, devoid of even a single noteworthy mutation or unique talent.
“Slicing you open for study wouldn’t yield half the data I get from breeding an offshoot Gillian-class Hollow at random.
It would be a waste of my time and a defilement of my instruments.”
“…”
Isshin froze.
The heroic martyr expression on his face calcified, then cracked piece by piece.
An indescribable cocktail of emotions surged within him.
Was it relief?
Or…
the sheer humiliation and irritation of being looked down on so utterly?
*I am the Captain of Squad 10, head of a branch family of the Great Noble Clans, and I’m not even worthy of being lab fodder?!*
The corner of Yanagawa’s mouth twitched.
He hadn’t quite expected Mayuri to react like that either, though it was certainly for the best—it spared him from actually having to sell Isshin out.
Mayuri paid no further heed to the emotionally devastated Isshin, returning his gaze to Yanagawa.
That little interlude seemed to have given him an alternative idea.
He tilted his head, his skeletal face mask producing a faint creak.
“However, Lord Yanagawa,” Mayuri resumed, his tone once again dripping with intrigue, tinged with a subtle, unexpected note of nostalgia, “since you are bound for the Soul King Palace to join Squad 0…
there is a small favor you might do for me.”
“Name it,” Yanagawa replied.
“Squad 0 houses a former superior of mine,” Mayuri said slowly.
“Kirio Hikifune.
The former Captain of Squad 12, and the founder of the theories behind the Gigai and Mod Souls.
“If you see her in the Soul King Palace, convey my regards.”
Yanagawa recalled the records he had perused in the Great Spirit Book Gallery; indeed, before her promotion to Squad 0, Kirio Hikifune had been Mayuri’s superior.
Watching this twisted, manic mad scientist exhibit such an unexpectedly human sentiment, Yanagawa understood.
He nodded in agreement.
“Very well.
When I meet Lady Kirio Hikifune, I will be sure to pass along Captain Kurotsuchi’s regards and news of your present endeavors.”
Once they finally stepped out of the Research and Development Bureau, Isshin let out a massive sigh of relief.
Wiping away phantom cold sweat from his forehead, he whispered to Yanagawa with lingering dread:
“Scared the living daylights out of me!
I really thought I was going to be left behind as a guinea pig…
Hey, Yanagawa, could you give a guy a warning before pulling a joke like that next time?!”