"The Ōken… It requires the sacrifice of over one hundred thousand souls from the World of the Living to allow a Shinigami to ascend to a higher level of existence."
"I'm not fighting for the Soul Society. I'm fighting for my family and friends who live in Karakura Town. If I back down now, and Yuzu, Karin, Tatsuki, Mizuiro, or Keigo are among those sacrificed…"
Ichigo gripped his Zanpakutō tighter. "So, Dad, teach me. Even if it means losing my powers, I have to fight."
"Very well." Seeing Ichigo's resolve, Isshin was reminded of Masaki, who had used herself as bait to defeat White, sacrificing herself to protect her family. "Masaki… Ichigo truly is your son."
He turned to Urahara and Yamamoto. "This technique requires four months of training. Even if Ichigo starts now, it won't be enough."
"Captain Shiba, Captain Urahara has already anticipated that." Tessai Tsukabishi's voice echoed as he appeared, followed by the Visored.
"Captain-Commander Yamamoto, we will create a time-distortion barrier. It requires a substantial amount of spiritual pressure to maintain. We'll need everyone's assistance to accelerate time within the barrier, allowing Ichigo to complete his training quickly. He has to stop Aizen before he reaches Soul Society. If he creates the Ōken there, using the souls of those within the replica Karakura Town, it will be too late."
"We have no other choice." Yamamoto turned to Ichigo. "We're counting on you, Ichigo Kurosaki."
"I understand."
Isshin and Ichigo stood in the center of the training ground. Tessai and Hachigen Ushōda sat facing each other, a barrier was forming around the two Shibas.
Yamamoto, Shunsui Kyōraku, Jūshirō Ukitake, Retsu Unohana, Toshiro Hitsugaya, Chōjirō Sasakibe, Shinji Hirako, Love Aikawa, Rōjūrō Ōtoribashi, and Kensei Muguruma unleashed their spiritual pressures, channeling them into the barrier.
Within the barrier, Isshin and Ichigo's movements accelerated, as if a film was playing at high speed.
Moments later, father and son sat facing each other, eyes closed. The onlookers sensed Ichigo's spiritual pressure fluctuating wildly. Then, it vanished.
Ichigo's Shinigami attire changed. He remained in his Bankai state, but the sleeve of his right arm was gone, the chain from his Zanpakutō now wrapped around his arm, embedded in his flesh, as if it had become a part of him.
The Shinigami channeling their spiritual pressure into the barrier felt a sudden drain on their reserves.
Crack! Crack!
As Ichigo stood, the time-distortion barrier shattered. The more spiritual pressure channeled into the barrier from the outside, the faster time flowed within. Conversely, the stronger the spiritual pressure within, the more external pressure required to maintain the distortion. Ichigo's transformation had overloaded the barrier, shattering it.
The Shinigami, exhausted from the exertion, collapsed to the ground, but a sense of hope filled them. The sheer amount of spiritual pressure required to sustain that barrier for even a short time suggested Ichigo had become incredibly powerful.
Kyōraku, looking at Ichigo, sensed a change in him. As their eyes met, he understood. A profound sadness now emanated from Ichigo, as if he had lost something precious. He glanced at the Zanpakutō, now fused with Ichigo's arm, and sighed, pulling his hat lower.
Every Shinigami knew the bond between a Shinigami and their Zanpakutō spirit was sacred. The Final Getsuga Tenshō, the technique that had granted Ichigo such power, had come at a steep price. Isshin's warning about losing his Shinigami powers had prepared Kyōraku for this. He had simply needed confirmation.
"Dad. Mr. Urahara. Lady Yoruichi. Mr. Tessai… And everyone from Soul Society… Don't worry. I'll defeat Aizen and end this. But first… I need to see Captain Ailin." Without waiting for a response, he vanished.
…
Ichigo reappeared atop one of the Sekkiseki.
"You're here, Ichigo." Ailin, sensing his arrival, turned to face him. "How are you feeling?"
"Sad. Empty…" Ichigo glanced at Zangetsu, now a part of him, then bowed. "Master Ailin, thank you for your guidance. Without you… I would have regrets."
Ailin's teachings had revealed the true nature of both White and Old Man Zangetsu, facilitating his mastery of the Final Getsuga Tenshō. However, he knew that without Ailin's help, without understanding the true nature of the two spirits within him, he would have carried the burden of guilt for rejecting White, who had only ever sought to protect him. He had mistaken his protector for a threat, a consequence of his own fear.
"I came to thank you, Master Ailin. You helped me find peace. But seeing you now… I realize just how strong you truly are."
Having merged with White and Old Man Zangetsu, Ichigo couldn't comprehend the extent of his newfound power. He knew he could now easily defeat Aizen. But against Ailin… he wasn't so certain.
"Do you blame me for not intervening?"
Ichigo shook his head. "Having reached this level, I understand you better now, Master Ailin. You didn't stop Aizen because he wasn't… worth fighting, was he? Not yet. But what was your plan? To wait until he created the Ōken, after sacrificing one hundred thousand souls?"
Ichigo's question reflected his own internal conflict. Ailin's guidance had allowed him to forge his two Zanpakutō, unlocking his true potential. But he also understood Ailin's desire for a worthy opponent. While he empathized, he couldn't condone the potential sacrifice of one hundred thousand lives.
"Who knows?" Ailin shrugged. "If Aizen, even after creating the Ōken, still isn't strong enough to pique my interest… I might not bother."
"Is that so?" Ichigo fell silent. "I understand, Captain Ailin. But I'm afraid I'll have to disappoint you. I'll defeat Aizen. In Hueco Mundo." Without another word, he vanished.
Ailin sighed, looking after him, his hand tightened on the Zanpakutō at his waist. Ichigo, having mastered the Final Getsuga Tenshō, was incredibly powerful. So powerful that Ailin had felt the urge to draw his own Zanpakutō, to fight him then and there. He had barely restrained himself.
However, Ichigo's current state, while powerful, wouldn't last. Ailin didn't want their fight to be interrupted by Ichigo's inevitable power loss. He would wait. He looked forward to facing Ichigo at his peak, after mastering Fullbring, after merging all four of his powers.
…
After a few flashes, Ichigo reappeared beside the waiting Shinigami.
"You're back, Ichigo." Kisuke Urahara looked up at him. "I've locked onto a Garganta in Hueco Mundo. Shall we depart?"
"Yes, please, Mr. Urahara."
"It's the least we can do." Urahara shook his head, approaching a crude stone archway. He channeled his spiritual pressure into it, and a black vortex appeared in its center. Ichigo stepped into the Garganta.
"Captain Urahara, do you mind if I tag along?"
Just when Urahara wanted to continue following Ichigo into Hueco Mundo, Ailin's voice sounded in his ears.
"Captain Ailin?"
The Shinigami exchanged uneasy glances. Ailin's actions were… confusing. He had fought against Aizen's forces, suggesting loyalty to Soul Society. But his earlier clash with Urahara and his allies indicated otherwise. They couldn't understand his motives.
"Wait, Captain Urahara."
Jūshirō Ukitake stopped Urahara as he prepared to follow Ailin. "Captain Urahara, while Ichigo is strong, Aizen is… resilient. You saw what happened. As a precaution, why don't you send us back to Soul Society first? We'll deploy our forces in the replica Karakura Town and prevent Aizen from creating the Ōken, from reaching the Soul King Palace."
"But Captain Ukitake, you can't open a Senkaimon…"
Urahara began, then paused, remembering Aizen's failed attempt to reach Soul Society through the Dangai. The Twelfth Division, it seemed, had taken their duties seriously, sealing all access to the Dangai from the World of the Living. But this also meant the Shinigami who had fought Aizen couldn't return.
"You're right, Urahara." Yamamoto, leaning heavily on his cane, approached them. "I didn't order the Senkaimon sealed. And Captain Kurotsuchi wouldn't abandon us. Something's happened in Soul Society. We have to return."
"Understood, Captain-Commander." Urahara turned to Tessai. "Give me some time. I need to retrieve some equipment from the shop." He and Tessai headed towards Karakura Town.
They returned minutes later, laden with equipment and quickly set up a makeshift lab. An hour later, Urahara, having analyzed the Dangai's seal, opened a Senkaimon.
"It's done, Captain-Commander Yamamoto. However, I don't have the clearance to lock onto the Seireitei's coordinates. This Senkaimon leads to Rukongai." A simple wooden frame appeared, its doors opened to reveal a white portal.