Soul Society, Tsunayashiro Clan Estate.
Keiko sat in her study, reading a medical book. With the influence of the Tsunayashiro clan, obtaining precious medical texts or inviting renowned masters was simple; she could even request lessons from the vice-captains or the captain of the Fourth Division. To master medicine, she had recruited numerous teachers and spent her days immersed in study.
Truthfully, no one in the three worlds could match her dedication and passion for cultivation. Most people in these realms were not particularly obsessed with becoming stronger; once they reached a certain height, they became stagnant—classic examples of individuals who believed they were top-tier figures but amounted to nothing in a real fight. Thus, Beltz could say with absolute certainty: among Shinigami, humans, Quincies, and Hollows alike, not a single person surpassed him in the effort put into cultivation.
Suddenly, she set her book down. "Since you've come, it's better to be open about it."
When no one answered, Keiko turned around and reached out. Her slender hand seemed to pierce through space itself. With a sharp tug to the side, space tore open like a curtain being pulled back. Standing behind the rift was a man wearing the captain's haori of the Gotei 13 and wearing glasses—Sosuke Aizen.
"Using only Kyokko without Kyoka Suigetsu... you're looking down on me a bit too much," Keiko said calmly. She wasn't surprised by his arrival in the slightest.
Aizen didn't seem surprised that she could see him either. He spoke softly, "Noren-Mekuri... a nostalgic technique."
The Kido Keiko had just used, "Noren-Mekuri", is a special Kido used to tear space and reveal camouflaged targets. This spell had broken the camouflage of Aizen's Bakudo #26: Kyokko. It brought back memories for Aizen; nearly a hundred years ago, his former captain, Hirako Shinji, had used the same move to uncover his Kyokko.
Aizen was also unphased that Keiko knew about his Kyoka Suigetsu. He continued, "The prerequisite for Kyoka Suigetsu is seeing its release. Since you aren't under hypnosis, there was no need to use it. However, with your current level of Reiatsu, you shouldn't have been able to detect my Kyokko."
Under normal circumstances, Keiko indeed lacked the ability to find Aizen. Unless she overthrew her "future" self, she was currently just a slightly stronger-than-average captain. But just because she couldn't see him didn't mean Beltz couldn't! Beltz was currently in the Wandenreich, watching the external surveillance monitors. He had seen Aizen approaching the Tsunayashiro estate, so Keiko, being forewarned and prepared, had no trouble spotting a Level 26 Bakudo.
"Eyes can deceive you, and spiritual senses can deceive you as well." Keiko showed no fear, even facing Aizen alone. After fusing with the Oken and the vast amount of Soul King fragments in her body, she could once again enter the state she used against Whitebeard. In that form, she possessed the Reiatsu of a released Zero Division member. Combined with the god-tier Zanpakuto, Enrakyoten, even Aizen wouldn't be her match—especially since she wasn't under the influence of his Perfect Hypnosis.
"I'm curious, how did you discover me?" Aizen asked.
"What you really want to ask is who I am, right?" Keiko chuckled. "You know the Seireitei like the back of your hand. Before that disaster broke out, you could confirm that no one like me existed here. The head of the Tsunayashiro clan couldn't be a nameless nobody. Yet, not only did I have no reputation before this, but there were also no traces of my existence at all."
"Indeed," Aizen nodded directly. "So, can you tell me who you are?"
"Of course." Keiko was quite friendly toward Aizen. Theoretically, they were in the same camp. From beginning to end, what was Aizen's ultimate goal? He had made it clear during the fight with Yhwach: he always acted to break anything that tried to control him. Simply put, Aizen hated having anyone above him. That's why he wanted to kill the Soul King and why he opposed Yhwach.
In this regard, Beltz was the same. He acted against everything attempting to control him. As for Aizen being a villain—if this world were still a manga, his actions certainly fit the part. Beltz had considered collaborating with him long ago, but he lacked the strength then. Collaborating with someone like Aizen without power was a recipe for being discarded. One had to stand on the same level as Aizen to be considered a partner—not just in strength, but in philosophy, wisdom, and overall capability.
Even though Yamamoto's strength was comparable to his, Aizen never viewed the Old Man as an equal. To Aizen, Yamamoto was someone he could treat as a subordinate whenever he wished; by controlling the Central 46 with Kyoka Suigetsu, he could issue orders that Yamamoto would follow like a pawn. In contrast, Urahara was someone Aizen truly acknowledged—not just for his strength, but for his terrifying intellect that surpassed Aizen's own.
So, Beltz had waited until now, until Aizen sought him out.
Keiko spoke coolly, "I am the 'Soul King Candidate' created by the Tsunayashiro clan."
"...A Soul King Candidate?" Aizen didn't seem shocked. He merely smiled slightly. "Interesting. No wonder you possess such fearsome power. Though, it surprises me that a creation like you would turn around and dominate the Tsunayashiro family."
"Isn't that how the world works? You think because you created something, you can dominate it, but it often explodes with power far beyond your grasp," Keiko said dismissively. "The Tsunayashiro clan wanted to control the three worlds by controlling the Soul King, but ambition without matching strength is merely a joke."
Aizen's smile widened. He could hear that Keiko wasn't just talking about the Tsunayashiro family; she was asking if he had the strength. Clearly, she was open to cooperation.
"If one's ambition didn't exceed the scope of their current strength, how could it be called 'ambition'?" Aizen replied. He knew better than to let her dictate the rhythm of the conversation. If he showed his strength just because she asked, he would fall into her pace and lose the initiative. In these moments, maintaining mystery was key.
Seeing Aizen unmoved, Keiko fell silent. The two shared a knowing look and, almost simultaneously, broke into smiles.
"I know your goal," Keiko said. "You want to kill the Soul King. That doesn't conflict with my own objectives. Shall we cooperate?"
"Oh? And how would we do that?"
"To kill the Soul King, one needs to assemble the powers of Shinigami, Quincy, Human, Fullbringer, and Hollow," Keiko said softly. "I have already obtained the powers of Shinigami and Fullbringer. What I lack are the Quincy, Human, and Hollow powers. I know you have the Hogyoku, which allows for Hollowfication of Shinigami and Shinigamification of Hollows. I need you to provide me with Hollow and Quincy powers, and in exchange, I can safeguard your future plans."
"Agreed," Aizen said. "However, I haven't conducted research into Quincyfication. That might take some time."
"I can wait." Keiko indeed could. This was part of Beltz's plan: he intended to eventually fuse his three bodies—Shinigami, Hollow, and Quincy. He had already put in significant effort, choosing the Munch-Munch Fruit, Dark-Dark Fruit, and Op-Op Fruit specifically for this future fusion. Before the final merge, he wanted each body to acquire the properties of the others to ease the process. This was why Erensig had recently become an Arrancar to gain Shinigami powers. The "Human-Human Fruit, Mythical Zoan, Model: Yhwach" currently in production would eventually be given to Erensig as his third fruit to grant him Quincy powers. Meanwhile, Keiko could gain Hollow powers through the Hogyoku, but Quincyfication required Aizen's research.
"I'll give you one more piece of information," Keiko added. "The Quincies have always existed. They are hidden right within the shadows of the Seireitei."
"...!" Aizen had remained calm through everything else, but this genuinely surprised him. Quincies hidden in the shadows of the Seireitei?
"Correct. Everything the Shinigami do is under their surveillance. They have been accumulating strength in the shadows until they have reached a level where they can crush the Shinigami," Keiko said. "If you want to study Quincies, you might try to see if you can enter that space."
Aizen didn't press her on the Quincies. Instead, he asked, "And the demons?"
When Keiko remained silent, Aizen continued, "Your Reiatsu shares a certain similarity with the demons that appeared in the Seireitei. Are they... Quincies?"
He hadn't thought so before, but after hearing about the hidden Quincies, it was a natural suspicion. Their appearances were always so sudden that even Aizen couldn't track them. If they were already inside the Seireitei's shadows, it made sense.
Keiko shook her head. "No. The first five monsters could be called Quincies, but the ones who appeared later are true demons. They come from the 'Abyss'—a type of biological entity independent of the three-world system. They won't interfere with your plans."
"I see..." Aizen pushed up his glasses. "Then, how did you obtain their demonic power? Your research into these demons seems quite deep."
Keiko smiled faintly. "I can tell you that as well. They possess a power called 'Devil Fruits.' Eating one grants a corresponding ability. I can give you some Devil Fruits, but in exchange, I need your Hogyoku. Just a temporary loan, of course."
Aizen appeared to think seriously about this. The Hogyoku was vital to him, but the one he currently held was incomplete. Trading it wasn't out of the question; he had created it himself, and even if Keiko reneged on the deal, he could eventually create another. Devil Fruits, however, were an entirely new frontier. He had obtained a blood sample from Whitebeard at the Bureau of Technology and had integrated demonic power into White Ichigo, but the samples were insufficient.
"Very well," Aizen said.
"Then let's make the trade in three days. Three Devil Fruits in exchange for a three-year loan of your Hogyoku. That shouldn't be a problem, right?"
Keiko wanted Aizen's Hogyoku so that Vegapunk could replicate it. Vegapunk had already collected data from the Hogyoku inside Rukia, but since it was a pinnacle of science from Bleach world, even he couldn't easily copy it. He needed the data from a second Hogyoku.