With each evolution, Ulquiorra Cifer's regenerative abilities had undergone a qualitative leap. From the basic healing of a Menos Pequeño, to the advanced regeneration of a Menos Grande, to the limb-regrowing regeneration of a Gillian.
Regeneration, surpassing mere "healing," allowed him to recover from even grievous wounds, given enough time. As an Adjuchas, his regeneration became rapid. As a Vasto Lorde, it became high-speed.
And after Aizen's Hōgyoku transformed him into an Arrancar, his high-speed regeneration evolved into ultra-speed regeneration. With this ability, as long as he wasn't killed by a single blow to the head and possessed sufficient reiatsu, he could recover instantly from any injury.
The wound he had just received was insignificant, a mere expenditure of reiatsu. However, Aizen, when assigning him the task of guarding the Hōgyoku, had instructed him not to interfere if anyone attempted to steal it.
Those two former Espada hadn't realized that even without their surprise attack, Ulquiorra would have allowed them to escape with the Hōgyoku. Their attack had merely provided him with a convenient excuse. While he didn't understand Aizen's motives, his duty was to obey. Aizen had his reasons.
…
Three Arrancar figures darted between the massive pillars of Las Noches. Unbeknownst to them, they were being watched.
Gin Ichimaru glanced at Ulquiorra in the main hall, then leaped onto the pillars, following the Arrancar.
As one of Aizen's top subordinates, while he wasn't entirely familiar with the Espada's strength, he knew Ulquiorra, chosen by Aizen for this important task, couldn't be weak. These three former Espada, even if they were Privaron Espada, couldn't have defeated Ulquiorra so easily.
The only explanation was that this was a trap laid by Aizen. He didn't know who the target was. Perhaps even he was a pawn in this game. But he had to play along.
Once they were far from Las Noches, Gin accelerated, appearing before the Arrancar.
The three Arrancar stopped abruptly.
"Damn it! It's Gin Ichimaru!"
"Number 103! What do we do?" The other two Arrancar panicked, turning to Number 103.
"My, my, three-digit Arrancar roaming around at night? Aren't you afraid of Lord Aizen's wrath? If I recall correctly, he sent all numbered Arrancar to intercept the intruders. Are you defying his orders?" Gin said with a sly smile on his face.
Number 103 was calmer than his companions, "Lord Ichimaru, we are patrolling Las Noches, as per Lord Aizen's instructions." He attempted to deceive Gin, but Gin, already aware of their actions, wasn't fooled.
"Really?" Gin raised an eyebrow. "But you seem to be coming from the direction of the chamber where Lord Aizen stored the Hōgyoku, not his personal quarters. Did you steal the Hōgyoku? Are you planning to escape?"
"How… how did you know?" The other two Arrancar's faces paled.
Number 103 expression darkened. Aizen was in Las Noches. The Hōgyoku had been stored in the main hall. There was no discrepancy in their direction. Gin's words meant he knew everything, that he had been waiting for them.
"Idiots!" he snapped at his companions. "Our plan has been exposed. We have no choice but to fight. Kill Gin Ichimaru, then escape!"
"You two, cover me!"
"Okay!" The three Arrancar split up, attacking Gin from different directions.
"Why bother?" Gin murmured, drawing his Zanpakutō. "Shoot to kill. Shinso!"
A white light flashed, slicing through several massive, reddish-brown pillars. The severed sections toppled to the ground, raising clouds of sand.
The three charging Arrancar were caught off guard.
"Impossible!" Number 103 coughed up blood, feeling his life force draining away. He clutched the Hōgyoku. "I acquired the Hōgyoku! With time, I could have surpassed Aizen, become the king of Hueco Mundo… How… how could I die here?"
"Hōgyoku… tell me… how can I use your power…" The Hōgyoku in his hand pulsed with a blue light, as if responding to his plea. But…
A white flash. A scream.
Number 103 hand, clutching the Hōgyoku, was severed. The gem's blue light faded. Unlike his earlier ambition, despair now filled his heart. The Hōgyoku, granting his wish, showed him true despair.
"Such a… peculiar thing." Gin bent down and picked up the Hōgyoku, holding it for the first time. "So this is what Aizen took from Rangiku's soul."
"It's not time to return you to her yet." He held the Hōgyoku to his chest, trying to sense Rangiku Matsumoto's presence within it.
"Ailin-sensei once told me that the Hōgyoku's power could extract a person's desires and manifest them into reality… Surpassing one's limits is also one of its abilities. So, Hōgyoku, if you can truly read my heart's desire, grant me the power to kill Sōsuke Aizen."
Boom!
A blue light enveloped the Hōgyoku, and Gin's spiritual pressure surged skyward, forming a blue and white pillar of energy.
…
In the Hueco Mundo desert, Ichigo Kurosaki, Chad Sado, Uryū Ishida, a small girl with a cracked Hollow mask, and two Hollows sat together. They had been in Hueco Mundo for over two days. Hueco Mundo, however, was far larger than Karakura Town. And with its endless desert landscape, they had no sense of direction.
Fortunately, on the second day, they had encountered Nell and her companions being attacked by Hollows. After rescuing them, they had asked for directions to Las Noches. Under Nell's guidance, they could now see the faint glow of the stars above Las Noches.
Suddenly, a powerful, oppressive reiatsu filled the air. It was so intense that even breathing became difficult.
They stood, looking towards the source of the pressure. A blue and white pillar of spiritual energy pierced the sky. Even from this distance, it was clearly visible.
"That reiatsu…" Ichigo sensed a familiar presence within it.
"Ichigo, do you know who that is?" Uryū asked, noticing Ichigo's expression.
"Yes." Ichigo nodded. "That's Gin Ichimaru, the captain who defected to Hueco Mundo with Aizen."
During his mission to rescue Shino Madarame in the Soul Society, Ichigo had fought Gin. That battle had been his first taste of defeat. Even White, taking over his body, had been unable to win. After Ailin's guidance, after acquiring his second Zanpakutō, Ichigo's strength had reached a new level. He had believed he had far surpassed Gin.
But now, sensing Gin's reiatsu, he realized they were equals. Gin, it seemed, was also a Shinigami at his limits.
A smile touched Ichigo's lips. This made things interesting. Perhaps because of his mastery over White, he found himself increasingly drawn to battle, especially against opponents of equal strength. He quickly suppressed his excitement, however. His priority was to rescue Orihime. He would enjoy a good fight after she was safe.
…
"Hmm? Is that an invitation?"
Two figures in captain's haori, sensed the surge of reiatsu.
Retsu Unohana's expression remained unchanged, while Zaraki grinned and started charging towards the source of the pressure.
"Captain Zaraki!" Isane called out, but Zaraki, eager to face such a powerful opponent, ignored her.
With Yachiru Kusajishi perched on his shoulder, pointing the way, he ran towards the depths of Las Noches.
"Don't worry, Isane," Unohana reassured her lieutenant. "With Captain Zaraki's strength, even if he encounters Captain Aizen, he won't be in danger." Her understanding of Zaraki was unparalleled. He was a natural-born warrior, a battle-hungry beast.
While Aizen's Kyōka Suigetsu could perfectly manipulate one's senses, it couldn't deceive instinct. Even under its influence, Zaraki's primal instincts would alert him to any danger, especially a life-or-death situation.
Aizen's attacks would be perceived, his illusions shattered. To defeat Zaraki, one needed either overwhelming strength and speed, or an ability like her own Bankai, Minazuki, a corrosive blood mist that reduced everything it touched to bone, leaving him nowhere to hide.
"Yes, Captain Unohana." Isane Kotetsu sighed.
She wasn't concerned about Zaraki. She was worried about herself and Unohana. While she knew Unohana possessed impressive Kidō skills, she was primarily a healer, not a fighter. What would happen if they encountered powerful Arrancar? Could she protect her captain? Doubt gnawed at her.
Unohana glanced at her distracted lieutenant, understanding her concerns. She chose not to address them, however. If Isane lacked confidence in her, let her worry. It would prevent her from panicking during a real battle.
…
"Gin?"
As Gin's reiatsu surged, Aizen's figure materialized on the throne within Las Noches' main hall.
His claim that he needed time to prepare for the Hōgyoku fusion had been a lie. He had been observing, waiting to see if Ailin would attempt to steal the Hōgyoku. Under Kyōka Suigetsu's influence, none of the Arrancar were aware of his presence. He watched their performance unfold.
Gin's intervention was both unexpected and… inevitable. After all, before joining Aizen, Gin had been Ailin's most prized disciple. Aizen had suspected Gin's allegiance, wondering if he was a pawn in Ailin's game. It seemed his suspicions had been correct.