Having given his instructions to Rukia and Renji, Byakuya Kuchiki vanished with a wave of his hand. He had cast Hadō #26, Kyokkō, a Kidō spell that created a cloaking field around him, bending light and rendering him invisible.
Sōsuke Aizen had used this same spell to tail Shinji Hirako, only to be discovered and his illusion dispelled with a single swipe. However, knowing Aizen's personality, that "discovery" had likely been a deliberate test.
At that point, Aizen had already reached the limits of Shinigami power. He was confident in his own abilities, and even more so in Kyōka Suigetsu's complete hypnosis. Hirako's continued vigilance despite the hypnosis had intrigued Aizen, prompting him to investigate. As Aizen himself had stated, it wasn't Hirako who chose him, but he who chose Hirako.
Cloaked by Kyokkō, Byakuya made his way to the Twelfth Division. His mastery of Kidō was such that only a captain, or a lieutenant with exceptional Kidō skills, could detect him. Having suppressed his spiritual pressure, he infiltrated Captain Mayuri Kurotsuchi's office undetected.
"Oh? A little mouse has wandered in. It seems the Twelfth Division's security requires… enhancement."
Kurotsuchi's office was less an office and more a personal laboratory. Byakuya's presence was instantly detected. As Kurotsuchi reached for his Zanpakutō, Byakuya dispelled the Kyokkō.
"Captain Kuchiki of the Sixth Division. To what do I owe this… unexpected visit?" Kurotsuchi paused, tilting his head inquisitively.
"I merely wanted to ascertain whether you were… genuine."
"Ha. What a tiresome question. I assure you, I am the genuine Mayuri Kurotsuchi. That imposter… I eliminated him. I even extracted his eyes and fashioned myself a rather convincing disguise. No one suspected a thing. It seems this… creator… lacks even a rudimentary understanding of science." He removed a colored contact lens, a flash of blue lightning briefly illuminating it.
The blue lightning confirmed Kurotsuchi's identity. The Reigai-Byakuya had mimicked Byakuya's distinctive blue spiritual pressure leaking from his eyes.
"Captain Kurotsuchi, the situation is dire. We need to undo the Dangai's seal and contact the captains in the World of the Living."
"That's impossible, Captain Kuchiki." Kurotsuchi replaced the contact lens. "I've already tried. The Kōtotsu has cleansed the Dangai, creating a two-week time lag between Soul Society and the World of the Living. Any captains returning through the Senkaimon will arrive two weeks from now. And any Senkaimon we open will lead to the World of the Living two weeks in the future."
As he explained, his fingers flew across the keyboard. "After… disposing… of the imposter, I managed to relay a message to the captains. The remaining forces in Soul Society are no match for these Reigai. You should find a safe place to hide and wait for the others to return."
"I understand."
Leaving the Twelfth Division, Byakuya glanced towards his aunt, Haruko Kuchiki's residence. A massive golden osmanthus tree now enveloped her courtyard, its branches laden with blossoms. Anyone approaching would be bombarded by the flower petals, each a projectile imbued with Kidō.
High above the Seireitei, Reigai-Ailin, clad in golden armor and his immense spiritual pressure staining the sky gold, seemed to sense Byakuya's gaze. He looked down, and for a moment, Byakuya was paralyzed with fear.
Fortunately, Reigai-Ailin seemed completely disinterested in him, and even in the impending battle between the Reigai and the remaining Shinigami. He was conserving his strength.
Once Reigai-Ailin's attention shifted, Byakuya gasped, relief washing over him.
"He's… too strong."
He had never experienced Ailin's spiritual pressure so directly. It was like staring into an abyss, its vastness threatening to consume him. Even without the other Reigai captains and lieutenants, Ailin alone seemed invincible, his power unmatched by anyone save perhaps his genuine counterpart.
Unable to bear the pressure any longer, Byakuya returned to the underground training ground, relaying Kurotsuchi's information to Rukia and Renji.
"Damn it!" Renji exclaimed, clutching his head. "That bastard used the Kōtotsu to create a time lag! The captains won't be back for two weeks!"
"What do we do? Just stand by and watch while those fakes deceive everyone? If they use this time to sabotage Soul Society, even if the captains return, it might be too late."
Rukia, Renji, and Byakuya agreed they couldn't remain idle. Two weeks was more than enough time for the Reigai to wreak havoc.
"Captain Kuchiki," Rukia said, "Captain Kurotsuchi mentioned the Dangai's current connection is to the World of the Living two weeks in the future. I'll go to the World of the Living and find some help. Perhaps we can bring the captains back sooner."
"Alright."
…
A white Senkaimon materialized in a park in Karakura Town. Rukia stepped out of the Dangai, relieved to sense several familiar spiritual pressures.
Without hesitation, she followed the familiar signatures and arrived at a row of small wooden buildings. A faded sign hung above one of them: "Urahara Shop."
She knocked gently on the wooden door. A young girl's voice called out, "Come in."
Rukia entered.
"Hello. Can I help you?" A young girl, no older than seven or eight, greeted her shyly. Her hair, parted in a V-shape, reminded Rukia of her own, though the girl's parted at her nose, while Rukia's parted at her forehead.
"Hello. I'm looking for Mr. Urahara."
Of Ailin's disciples, Rukia hadn't spent the most time with him. However, due to her relationship with Hisana Kuchiki, Haruko Kuchiki had treated Rukia like family, often inviting her for dinner. Rukia had heard many of Ailin's stories, including those about Kisuke Urahara and his childhood friend, Yoruichi Shihōin.
She had come to the World of the Living seeking Urahara's help. Ailin considered Urahara a more skilled scientist than even Mayuri Kurotsuchi.
"Mr. Urahara? One moment, please." The girl bowed and disappeared into the back room.
Moments later, Urahara and Tessai Tsukabishi emerged. A black cat sat perched on Urahara's shoulder.
"Captain Urahara. Grand Kidō Chief Tsukabishi. Lady Yoruichi." Rukia bowed respectfully.
"Well, well. I heard magpies this morning. It seems they heralded your arrival, Captain Kuchiki." Urahara greeted her with his fan hiding his smile.
Ever since learning of Ailin's broader perspective, Urahara's wariness had faded. He now saw Ailin as a valuable asset to Soul Society, a mentor to several of the Gotei 13's strongest captains. At least half of the current captains had been trained by him. His contributions far outweighed Urahara's own.
"Captain Kuchiki, to what do we owe this pleasure? Does Captain Ailin require our assistance?" Though he doubted Ailin needed anything from him. The battles against Ichigo Kurosaki and Aizen had demonstrated the vast gulf in their power.
"No, it's not Master Ailin. In fact, none of the captains have returned to Soul Society." Rukia sat across from Urahara. "While I'm speaking to you now, my present… is two weeks in the past."
She then explained the events that had transpired after the captains left for the World of the Living, including Captain Kurotsuchi's assessment of the Dangai's temporal distortion.
"Captain Urahara, according to Captain Kurotsuchi, the mastermind used the Kōtotsu to erase two weeks from the Dangai's timeline. If I return through the Senkaimon, I'll arrive two weeks in the future. I've come to ask for your help. Can you undo the Kōtotsu's effects and bring the captains back?"
"I see. To manipulate the Kōtotsu to such a degree…" Urahara thought. "The Kōtotsu stabilizes time within the Dangai. Encountering it can create temporal discrepancies… This mastermind's understanding of the Dangai surpasses even my own."
From Rukia's brief account of Kurotsuchi's findings, Urahara deduced that, while the mastermind's combat abilities were unknown, their scientific prowess was exceptional. He himself hadn't achieved such mastery over the Dangai.
"Captain Urahara, we don't have much time…"
"Of course. Don't worry, Captain Kuchiki. I'll investigate the Dangai's temporal fluctuations and see if I can restore the timeline. Stay here for now. Once I've resolved the issue, we'll return to Soul Society together."
"Thank you."
…
After a short while, Rukia left the shop. Urahara, assisted by Tessai, had erected a large Kidō barrier around the underground training area, clearly preparing for a complex experiment. Without the SRDI's resources, Urahara had to improvise. Fortunately, his Bankai, Kanonbiraki Benihime Aratame, allowed him to manipulate matter, creating the equipment he needed.
Having released his Zanpakutō, he began constructing a device to connect to the Dangai, to unravel the Kōtotsu's manipulation of time.