The thought excited Yoshio. Maybe it was all the time spent with Aizen and Urahara, or his own research with Angra and Baelz—he'd picked up a scientist's itch: a love for the unknown. He wanted to see what would happen if the Blade were used on Soul King power.
So he moved immediately.
…
After returning to Soul Society with Aizen, Yoshio went to find Jūshirō Ukitake.
Post-retirement, Ukitake had moved back to his clan estate, but he sometimes visited Thirteenth Division's Ugendō—the former captain's room he used. After he stepped down, Hitsugaya didn't take the space, expanding his former lieutenant's office instead. Ugendō remained for Ukitake to return and advise whenever he wished.
At the moment, Ukitake was at Ugendō Quarters.
Ugendō sits over a pond—breezes stirring ripples. A figure stood before the house, gazing into the water's mirror. Dressed in white, Ukitake wore a gentle melancholy as he watched the ripples reflect his refined features. Birds skimmed the surface, drawing elegant arcs. He tilted his head, looking into the distance, lost in thought. His heart seemed calm as a lake, yet layered with quiet waves—until a smile touched his lips.
"Yoshio!"
He waved. "What brings you here?"
Yoshio, carrying some fruit, sat down. "Off work and free, thought I'd drop by."
He added, "You looked a bit troubled. Something on your mind?"
"The World of the Living… I've heard," Ukitake sighed. "More has happened in the last hundred years than in the previous several centuries."
Yoshio smiled. "Leave that trouble to us. You just focus on your health. Who knows—you might be called back one day."
"I hope that day never comes," Ukitake said. "Come inside."
The room was sparse; Ukitake had moved many things back to his clan. He brewed tea and said, "Good timing—you can advise me on some writing issues."
"That's partly why I came. I'm not sure what to write next," Yoshio said. "The Central 46 halted my Thousand-Year Blood War—I need a new serial."
After years, the story had reached the Egghead arc—the crew heading to the world's top scientist's base. But the Central 46 forced it to stop for sensitive content.
Ukitake knew and chuckled. "I warned you—your material is too sensitive. Consider your status; what you say carries political weight. The negative impact on youth is incalculable."
"Come on, it's just for fun—who knew those old men were so touchy?" Yoshio waved it off. "Anyway, I was thinking of retiring, but Hisagi keeps pestering me to start a new one."
"Without you, sales of Seireitei Communications would halve. No wonder Hisagi is anxious… So, new ideas?"
"Yeah. I even have a title: Lord of the Mysteries."
"Sounds like folk horror?"
"Not exactly. Here, let's hash it out."
Once they got going, they couldn't stop—talking through dinner and into the night. Ukitake offered Yoshio a room, and he stayed, planning to continue tomorrow.
…
Late at night, moonlight spilled through the half-open curtain, painting a pale glow. Yoshio opened his eyes, stood, slid open the door, and entered Ukitake's room.
"You're fast, Captain Aizen," he said to Aizen inside, who had already wrapped the area in Kyōka Suigetsu's silence.
"I heard your conversation," Aizen said. "I'm curious about your new book. Do your best."
"Is that so?" Yoshio smiled, drew the Mind-Rending Blade, and said, "We can discuss that after. Let's test our hypothesis."
He slashed Ukitake.
They watched closely. Darkness welled up from Ukitake's body; as it was about to take shape, Aizen shifted the space. In an instant, Yoshio, Aizen, and the mass of darkness appeared in Hueco Mundo.
Stimulated by the environment, the darkness swelled faster.
Boom!
A vast spiritual pressure erupted, strong enough to make the world tremble. Endless darkness rippled outward, making the already dim Hueco Mundo even more ominous.
Nearby Gillians were stained black through and through, bodies melting into the dark. Even distant Adjuchas and Vasto Lorde-class Hollows—and Arrancar in Las Noches—felt something peculiar and powerful.
Starrk and Lilynette felt a pang and looked out toward the source.
"Starrk…" Lilynette asked, "What's… happening over there?"
"Not sure," he murmured. "But it feels like Hueco Mundo is about to change."
Szayel, mid-experiment, also paused, unsettled.
Baraggan, Harribel, Nelliel, Ulquiorra, Yammy, Nnoitra, Grimmjow—every Arrancar stilled.
The stronger the Hollow, the deeper the resonance. It felt as if Hueco Mundo…
Was about to be remade.
Amid the pouring darkness, Yoshio and Aizen alone retained any color, observing the transformation. After the blackness spread, it grew… bleached—turning chalk-white.
It was a hand. A giant's hand—too pale—with a mouth upon it. As it emerged, it growled, speaking in a language not of the three realms.
Yoshio was surprised.
Strange. Given Ukitake's traits, the split should have been a female Quincy, with the Soul King's right hand replaced by… the Hollow King's left arm?
But now it's just… a left arm.
If inverted, there should have been a Quincy body carrying a left hand. Who's going to fill my female Quincy slot now?
He soon understood—and so did Aizen.
"The primeval Hollow that devours worlds would naturally consume everything," Aizen murmured. "The Quincy that should have appeared was devoured the instant it split."
The Soul King is a Quincy—and more. His opposite wouldn't simply be a Shinigami.
Clearly, the opposite is the Hollow King.
Not Baraggan. Rather, in the primordial era: the world-devouring Hollow that would have consumed the chaotic world—the Devourer.
The Soul King exists to halt that Hollow. If it can eat worlds, it can certainly eat a Quincy. Thus, the Quincy opposite split from Ukitake was swallowed immediately by the Hollow King's left arm.
Who would have thought that the Hollow King—who never fully emerged in the chaotic world—would be born now. Even if only a left arm—for now. If he used the Blade on other Soul King parts, could he assemble a Hollow King?
But… was it useful?
Yoshio eyed the white arm doubtfully. The Hollow King's left arm radiated endless hunger, as if it would devour everything around it.
You'd dare implant that?
Soul King fragments confer benefits in a body—unique abilities, reiatsu boosts. Even if a Shinigami can't fully utilize them, forced integration still helps.
But this thing?
It looked nothing like a Soul King fragment. Implant it, and you might get eaten.
"Rrraah!"
The left arm fully formed; the darkness cleared, and the world brightened a little—relative to before. In truth, Hueco Mundo grew darker. There's no sun there, only the moon's faint glow. Now it dimmed further, the decay, desolation, and withered breath deepening.
"Rrraah!"
The pallid left arm emitted a strange roar and fired a red beam at Yoshio and Aizen—from the mouth on its palm. Like a Cero, but on a different level—the true Cero Oscuras of a king.
One such blast could rival the combined Ceros of the Espada.
Even Yoshio and Aizen had to avoid a direct hit. But even after dodging, countless red beams tracked Yoshio.
"Troublesome…"
Yoshio extended a finger—Mirror Rebound.
A mirror manifested before him, catching the unavoidable blast. After a clash of forces, the Cero snapped back toward the left arm.
Boom!
The reflected blast moved even faster and slammed into it, detonating a storm of spirit-sand. More beams rained down. Amid the thunder, Yoshio burst from the explosion, scorched in places but unhurt—thanks to Hinamori's ultimate defense.
"Captain Aizen, this thing's no pushover," he called.
Aizen frowned, then raised his hand. "Hadō 99: Goryūtenmetsu."
Without incantation, five dragons of surging reiatsu roared forth. Aizen cast the ninety-ninth Hadō without chant—and with overwhelming force.
In a heartbeat, the dragons crashed into the left arm, triggering a massive explosion and shaking the region.
Yoshio couldn't keep spectating; this wouldn't be easy. Aizen alone might not suffice. He pressed his palms together, conjuring a massive blizzard—and simultaneously, a flame storm. Snow and fire together, contradictory forces amplifying each other beyond mere addition.
In the end, it was only the Hollow King's left arm. It might not even handle one of them—let alone both.
It must have been blinded by its devouring instinct!