Under a bright moon and sparse stars, the desolate mountains west of the Rukongai loomed deep and foreboding in the night.
A pale gray mist rose from the valley floor, creeping over the jagged rocks and shrouding the entire ravine in a hazy, ghostly white. Several layers of barriers cut the area off from the outside world, tightly locking any fluctuations of spiritual pressure within the ravine.
Tosen Kaname stood before the workbench, facing an array of complex instruments and spell matrices. The light from the reishi lamps cast a gray glow over his dark complexion. Tracing his fingers across the matrix, he channeled his spiritual pressure into the dense network of nodes, adjusting the data over and over again. He had already lost count of how many times he had tried.
Ever since Hasumi Ren had hurriedly left that day, he had been coming here every day to test it. He tried to replicate Ren's spell matrix, trying to uncover whatever it was that Ren had hidden back then. He remembered Ren's behavior vividly. It wasn't the irritation of a failed experiment, but a deeper sense of shock and bewilderment. That hesitation, that look of wanting to speak but holding back—he remembered all of it.
It was a spatial anchoring experiment. Ren's reaction couldn't have been caused by a simple technical glitch; he must have discovered something else entirely. Yet, Ren chose to conceal it, brushing him off with a casual excuse about a minor issue with the experiment.
Tosen's fingers tightened slightly. He was deeply dissatisfied with Ren's attitude and secrecy.
Taking a deep breath to suppress his rising frustration, Tosen channeled his spiritual pressure into the spell matrix once more. Spatial nodes, spiritual pressure anchoring, Hueco Mundo coordinates—everything appeared completely normal. He adjusted several parameters in an attempt to expand the detection range, but the unfamiliar spatial fluctuation never manifested.
There was absolutely nothing.
Griting his teeth, he tried a few more times, but each attempt ended in failure. Tosen's breathing grew ragged, and fine beads of sweat formed on his brow. After an unknown amount of time, he traditions slammed his clenched fist heavily against the machine.
A dull metallic thud echoed through the ravine, startling a few birds resting on the distant treetops. They flapped their wings and took flight into the night sky, their hoarse cries fading into the mist.
Tosen stood frozen, his chest heaving heavily. His fist remained pressed against the metal casing. A dull ache throbbed in his knuckles, but he didn't pull away. He simply stood in silence amidst the darkness, like an abandoned stone statue.
Before long, footsteps approached from behind. They were light and slow. Tosen's brow twitched slightly, and he turned around.
"Lord Aizen."
Aizen stepped out from the mist. He glanced at Tosen, then at the dented equipment. "What happened?"
Tosen lowered his head and remained silent for a moment. He was hesitating. Should he report Ren? He had no proof. Ren had never explicitly stated that he found anything; all of Tosen's suspicions were merely conjectures. With nothing but groundless words, how could he bring this to Lord Aizen?
"What is it? Is it something difficult to speak about? Kaname, between the two of us, there is no need for secrets. Just speak freely." Aizen's voice reached him again, as gentle as ever.
Tosen grit his teeth. "Lord Aizen, I do have a concern, but I am uncertain how to phrase it."
"Speak."
Tosen took a deep breath. "It is regarding Hasumi Ren."
Aizen's brow twitched slightly. "Ren? What about him?"
Tosen recounted the details of that day's experiment exactly as they had unfolded. How Ren had suddenly stopped in bewilderment, and then hurriedly concluded the experiment, claiming it was just a technical issue. But Tosen suspected that Ren was hiding something.
"I have no evidence, nor can I be entirely certain. It is just... Ren's reaction at the time did not seem like someone facing a mere technical glitch." Tosen's voice was low. "I believe he may have discovered something unusual, but I cannot confirm what it specifically entails."
Aizen listened quietly, falling silent for a brief moment. "So, you have been testing here for days just to uncover what Ren has been hiding?"
Tosen bowed his head. "Yes. However, my abilities are limited, and I have been unable to replicate it."
Aizen walked over to the workbench, inspecting the dense data and spell nodes. He said nothing, merely observing them silently for a while. Then, he turned around to face Tosen.
"You do not need to investigate this matter further."
Tosen blinked in surprise. "Lord Aizen..."
"I will ask Ren myself," Aizen replied calmly. "You have nothing to worry about. You did well to bring this to my attention."
Tosen's lips parted as if to say something, but he ultimately just bowed his head. "Understood."
Aizen patted his shoulder and turned to walk out of the ravine. His figure gradually dissolved into the night, leaving only the reishi lamps flickering faintly through the mist.
Tosen stood where he was, remaining silent for a long time. Then he turned and walked back to the workbench. He no longer tweaked the data, but simply stood there quietly, like a statue. The night wind swept through, rustling the hem of his clothes as they fluttered gently in the mist.
A few days later, in the secret laboratory.
Aizen sat at the desk, several documents spread out before him. Before long, Hasumi Ren appeared behind him and stepped up to the desk.
"You requested my presence."
Aizen looked up at him. "Have a seat."
Ren took a seat across from him.
Aizen slid a document over. "This is the progress report for the Hogyoku's development. Take a look."
Ren's hand paused momentarily before he picked up the file and flipped through it. It was filled with dense figures, intricate spell structures, and records of spiritual pressure fluctuations he had never seen before.
"Your Garganta project is progressing much faster than I anticipated," Aizen noted from across the table. "Your mastery over spatial spells has also exceeded my expectations."
Ren set the document down. "You flatter me, Vice-Captain Aizen."
Aizen shook his head. "No need for modesty. You have proven your worth. Therefore, I have decided to let you join the development of the Hogyoku."
Ren's brow twitched slightly.
The Hogyoku. That was Aizen's most core secret, the cornerstone of his entire grand design. Aizen had mentioned it before, but Ren had assumed it was merely an empty promise. He hadn't expected it to materialize so soon.
"Of course," Aizen turned his gaze squarely onto him, "this project has always been under my direct supervision, with Tosen assisting me. While your abilities are sufficient, you still lack experience. As such, Tosen will guide you initially so you can observe and learn. Once you have gained enough experience, I will assign you more critical tasks."
Ren nodded. "Understood."
With a nod from Aizen, Ren began reviewing the papers in his hands. But right then, Aizen spoke up abruptly.
"Ren, regarding the spatial anchoring test during the last Garganta experiment... is there anything you would like to tell me?"
Ren's fingers froze mid-page. He raised his head to look at Aizen. The warmth in those eyes had vanished, replaced by a calm, unyielding gaze that brooked no evasion.
"What do you mean by that, Vice-Captain Aizen?"
Aizen remained silent, watching Ren intently while his fingers tapped the desk in a slow, deliberate rhythm. The atmosphere grew increasingly tense.
Yet, Ren did not avert his gaze. He looked directly into Aizen's eyes, his expression completely blank. His breathing remained steady, his heartbeat perfectly regular. Everything about him was normal.
"It was merely an issue with the experimental data," he finally spoke, his tone casual and flat, as if discussing something trivial. "There was a minor misalignment in the connection of the spiritual pressure nodes, which caused the sensory data to fluctuate. I have already recalibrated it, so it won't affect any subsequent tests."
He paused. "May I ask what exactly you were referring to, Vice-Captain Aizen?"
Aizen stared at him for a moment before offering a smile. "Is that so? Then it seems I must have misunderstood."
Ren lowered his head. "You overstate it, Vice-Captain Aizen."
Aizen waved his hand dismissively. "Do not pay it any mind. You have been working hard lately; go back and get some rest."
"Thank you, Vice-Captain Aizen." Ren stood up and walked toward the door.
Behind him, Aizen sat at his desk, his gaze deep as he watched the door click shut.
Ren's performance just now had been absolutely flawless. His expression, his tone—not a single flaw could be found. If he really had discovered something, his acting was nothing short of perfection. If he hadn't, then Tosen's suspicion was entirely baseless.
Aizen's fingers lightly tapped the desk once more. He had no proof, nor could he determine if Ren was lying. But that didn't matter. Ren's value lay in what he could accomplish. Garganta technology, spatial spells, Hollowfication abilities—these were all tangible, undeniable achievements.
Furthermore, Ren's stance was crystal clear. He hadn't denied anything, nor had he admitted to anything; he had simply deflected the question entirely. This calm, unyielding composure actually made Aizen appreciate him all the more.
He didn't need to resort to coercion to control Ren. Coercion only bred resistance, whereas mutual benefit and trust would ensure someone followed willingly. What Ren needed right now was time and space to make his own choice.
Aizen retracted his gaze, picked up the documents on his desk, and resumed reading. As for what Ren was hiding... he would find out sooner or later.
Walking back to the Fourth Division quarters, Ren recalled Aizen's expression from moments ago. Aizen's eyes, his tone—every single detail had signaled to Ren that Aizen knew something was amiss.
But Ren had gambled and won. Without concrete proof, Aizen would never make a move against someone so valuable. Ren took a deep breath, forcing himself to calm down.
A few days later, in the underground cavern beneath Sokyoku Hill.
Ren traversed the hidden passageway and stepped into the cavern. His footsteps suddenly halted.
The cavern had changed drastically. The spiritual pressure isolation barrier had been significantly upgraded, locking any fluctuations completely inside the cave so that not even a shred could leak out.
The division of sectors was also much clearer. The large open clearing from before remained untouched, the jagged sword cuts and charred Kido marks from his training with Unohana still scoring the rocky walls. However, on the opposite rock wall, a brand-new independent chamber had been excavated, sealed away behind a transparent barrier.
Kisuke Urahara stood inside that separate space with his back to Ren, tinkering with several instruments while reviewing the experimental data in his hands.
Ren drew closer, stepping through the barrier to observe the dense streams of data and spell nodes on the devices. With his current insight and technical expertise, he could just barely grasp what was happening.
The experiment Urahara was conducting was an incredibly stealthy form of spatial detection technology. Ren's brow twitched as the realization struck him instantly. Urahara already had a working theory on how to reverse-engineer a lock on the Wandenreich's location, and he was currently refining the technology. If he succeeded, he would be able to peer inside that hidden space and definitively confirm what lay within.
To develop a comprehensive strategy and experimental blueprint in such a short timeframe... Kisuke Urahara truly was a terrifying individual.
Sensing Ren's presence, Urahara turned around with a characteristic smile. "You're here? Come, take a look at this blueprint for me."
Ren walked over to the workbench, and Urahara slid a document filled with experimental procedures and spell node diagrams toward him.
"This is the spatial detection spell I designed," Urahara explained, pointing to several nodes on the schematic. "The principle relies on using spiritual pressure shockwaves to graze the barrier of that space, then reverse-calculating the internal structure based on the feedback frequencies. Take a look. See any flaws?"
Ren picked up the document and reviewed it meticulously. The spell matrix was brilliant, and the underlying logic was flawlessly clear. Instead of attempting to forcefully tear open the spatial barrier, Urahara was using a far more covert and secure method to perceive its existence. It was akin to using sonar to map the ocean floor—no physical contact, no disturbance, prioritizing absolute stealth.
"It's a very ingenious approach," Ren said, setting the papers down. "I can't find any faults with it."
Urahara grinned. "Good to hear. Given a bit more time, I'll be able to confirm exactly where that space is located and what it contains."
Ren looked at him steadily. "Are you about to begin the exploration?"
Urahara nodded. "Exactly. If I uncover anything, you'll be the first to know." He paused, turning back toward the instruments. "Ren, have you ever thought about what might actually be hiding inside that space?"
Ren fell silent for a brief moment. "I don't know. But whatever it is, the fact that it has remained hidden silently right beneath the Seireitei for so long means it's not something we can easily afford to provoke."
Urahara nodded in agreement. "You're right. That's why I'm only scanning it for now. Once we figure out exactly what we're dealing with, we can make more detailed plans."
Ren nodded, offering no further comment. He turned and walked out of the separate chamber, stepping into the open clearing at the center of the cavern.
The scars of his training with Unohana still remained—slashes from blades and craters from spiritual pressure detonations. Standing amidst those remnants, he gazed at the deep fissures scoring the rock walls. Now, there were many fresh craters carved out by hand-to-hand combat.
Yoruichi had already scheduled their next sparring session, making his daily itinerary feel tighter than ever.
'I wonder... if Captain Unohana notices something when the time comes, will she ask about this?' 'And if she does, how am I supposed to answer...?'
From behind, Urahara's voice rang out. "Ren."
Urahara stood at the threshold of his chamber, holding a document, a rare look of gravity on his face. "Come to think of it, credit for this entire development goes to you. No matter what turns out to be inside that space, thank you for telling me."
Ren shook his head. "No need. After all, we're in the same boat now."
Ren withdrew his gaze, gave a casual wave, and turned to walk toward the cave exit. His expression remained completely serene, but within his mind, a torrent of thoughts was churning.
Urahara's detection spell, Aizen's suspicion, and that hidden space tucked away in the shadows of the Seireitei... All the threads were converging on a single point, and he happened to be standing right at the intersection.
With all these pieces in place, something could certainly be done.
Lost in thought, Ren strode forward into the darkness.