The Power of Kenbunshoku  

Uncle Ailin, a seasoned captain, possessed a wealth of knowledge far surpassing what Nanao could gather through her own investigations. The possibility of him deceiving her never crossed her mind.

"Of course," Ailin confirmed, drawing a circle roughly two meters in diameter around himself with a wave of his hand. "Nanao, begin."

Fusing one's reiatsu with Kidō-type spiritual pressure resulted in a temporary boost in power. However, the enhancement from Bakudō (Binding) type was far less dramatic than that of Hadō (Destruction) type.

Still, Bakudō was significantly gentler than Hadō. The manifestation of "Kenbunshoku" wasn't as explosive as "Shunkō," but rather, it exuded an air of effortless grace.

With those words, Ailin's body shimmered with a soft white light, and a gentle breeze emanated from him, spreading outwards. Though his eyes were closed, the underground base manifested within his perception in even greater detail.

"Alright, Uncle Ailin, be careful. Here I come!"

Taking a deep breath, Nanao began chanting a Kidō incantation. Typically, she prioritized silent Kidō in combat to swiftly gain an advantage or secure victory. However, Uncle Ailin's challenge required her to force him outside the circle within fifteen minutes. With the circle's diameter being a mere two meters, she only needed to employ attack Kidō with a range exceeding that distance.

"Oh Lord! Mask of flesh and bone, flutter of wings, ye who bears the name of Man! Truth and temperance, upon this sinless wall of dreams unleash but the claws of thy beast..."

"Hadō #33: Sōkatsui!"

As Nanao chanted, a massive blue fireball formed in her hand, surging towards Ailin with remarkable speed.

In Ailin's perception, Nanao's every move – from raising her hand, to chanting the incantation, to the very arrangement of the Kidō particles – unfolded before him with heightened clarity.

Thus, as the Sōkatsui fireball hurtled towards him, Ailin gathered his own reiatsu, shaping it into a similar form. Extending his hand towards the incoming attack...

Poof—

The Sōkatsui met Ailin's reiatsu, and like a deflating balloon, its blue flames rapidly dissipated. Ultimately, it dissolved into harmless particles within Ailin's palm, leaving him completely unscathed.

"Is that... Hanten Sōkō?"

Nanao gasped. After two months of training with Uncle Ailin, she was confident in her Kidō prowess, rivaling even the most skilled Kidō specialists within the Kidō Corps.

Hanten Sōkō, or "Counter Kidō," was an advanced technique achievable only by those who had reached an exceptional level of mastery and grasped the true essence of Kidō. It surpassed even silent casting and post-incantation casting in complexity.

As the name implied, Hanten Sōkō involved releasing one's reiatsu with a particle arrangement opposite to that of the incoming Kidō attack, effectively neutralizing it.

Nanao wasn't surprised that Uncle Ailin could perform Hanten Sōkō. What shocked her was his ability to instantly analyze the intensity and particle arrangement of her Kidō with his eyes closed, relying solely on the perception of "Kenbunshoku." It demonstrated an almost terrifying level of Kidō mastery.

Determined to press on, Nanao used Shunpo to circle around Ailin, creating a flurry of movement to mask the fluctuations of her reiatsu as she cast Kidō.

She unleashed a barrage of Hadō and Bakudō, employing various techniques like silent casting, post-incantation casting, and even double chanting.

However, no matter what she threw at Ailin, his surroundings would shimmer with a corresponding reiatsu, effortlessly negating her attacks. From an outside perspective, it appeared as if the two-meter radius around Ailin had become a forbidden zone for Kidō.

Bang, bang, bang...

Each faint sound marked the nullification of a Kidō spell.

"Uncle Ailin, you're incredible!" Nanao exclaimed, feeling a sense of awe mixed with frustration.

Hanten Sōkō... Even the Grand Kidō Chief of the Kidō Corps wouldn't be able to perform it so continuously, right?

Every individual possessed unique reiatsu strength, chanting habits, and particle condensation levels. In other words, even if two people cast the same Kidō spell, their reiatsu intensities and particle arrangements would differ.

Only by having a profound understanding of the enemy's reiatsu and particle structure could one effectively counter their Kidō using Hanten Sōkō. Otherwise, the mismatch in reiatsu intensities and particle structures would result in a more powerful explosion, causing greater harm to the user of Hanten Sōkō.

Yet, within these ten minutes, Nanao had cast over a hundred Kidō spells. And every single one, upon entering Uncle Ailin's vicinity, had dissipated like a fragile bubble.

Was this truly something a human soul could achieve?

Even Nanao, after casting so many Kidō in succession, was exhausted and gasping for breath.

Looking at Uncle Ailin, who had remained motionless since the timer started, a feeling of dejection settled upon her.

With a flash, Nanao used Shunpo to appear before Ailin and launched a Hakuda (Hand-to-Hand Combat) attack. Since Kidō was ineffective against Uncle Ailin's Hanten Sōkō, perhaps Hakuda would fare better?

However, something even more astonishing occurred.

Uncle Ailin seemed to anticipate her every move. Often, as she lifted her leg to kick, he would take a step back, her attack passing harmlessly in front of him. She threw a punch, he sidestepped, leaving her striking at empty air.

No matter how she attacked, Uncle Ailin's response was always one step ahead.

Five minutes later, Nanao rested her hands on her knees, gazing at Ailin, who appeared unfazed by her efforts. She rose with a wry smile.

"I'm sorry, Uncle Ailin. I lost."

"Hey, don't be so disappointed, Nanao," Ailin chuckled, opening his eyes and patting her shoulder. "This is one of my secret techniques. If I couldn't even dodge your attacks, why would I bother teaching it to you? That would be a waste of your precious training time, wouldn't it?"

"You're right." Nanao's spirits lifted at his words. If she could master this powerful technique, she wouldn't need Uncle Ailin or Uncle Kyoraku's help to avenge her father once she discovered his killer.

...

"Sigh... I've practically searched the entire Rukongai, yet I still haven't found Momo Hinamori or Toshiro Hitsugaya..."

Ailin soared through the sky above the Rukongai, his speed steady and unhurried.

After concluding Nanao's training, Ailin decided to put his plan of finding promising children into action. However, despite scouring almost every corner of Soul Society, he had even located Rukia and Renji Abarai, but Toshiro Hitsugaya and Momo Hinamori remained elusive.

"Perhaps, Shiro-chan hasn't been born yet..." He thought, shaking his head as he turned back towards the Seireitei.

Undoubtedly, if Ailin had to choose a child to raise, Toshiro Hitsugaya would be his top pick. Failing to find him was undeniably a disappointment.

But Ailin wasn't one to give up easily. After all, if one path was blocked, there were always alternative routes.

"If I recall correctly, the first to discover Toshiro Hitsugaya's unusual reiatsu was Rangiku Matsumoto..."

"It seems I'll have to ensure Haruko gets closer to Rangiku Matsumoto. That way, once Rangiku encounters Toshiro Hitsugaya, I can bring him back from her as soon as possible."

Even if it took a little longer, it wouldn't matter. He just needed to keep an eye on the Shin'ō Academy in the future.

"Hmm?" At that moment, Ailin paused, sensing a familiar reiatsu.

"Interesting..." A smirk appeared on his face as he changed course, his body transforming into a streak of light, tearing through space towards another location.

Swoosh!

...

In a small forest clearing, Gin Ichimaru and Kaname Tōsen stood observing as Sōsuke Aizen held a blue, diamond-shaped crystal. Its light illuminated a Shinigami kneeling before Aizen, his body gradually becoming encased in white, bone-like armor.

"Roar..."

As a Hollow mask completely covered the Shinigami's face, he let out a Hollow's roar. His reiatsu erupted, forming invisible shockwaves that bent the surrounding trees.

However, despite their intensity, these shockwaves merely caused the captains' haori to flutter as they reached Aizen and his companions, having no effect on them.

"Another failure..." Aizen sighed, gazing at the Hollowfied Shinigami who had lost all reason.

Every time his experiments yielded unsatisfactory results, Aizen couldn't help but think of his former captain, Shinji Hirako.

Undeniably, as a test subject, Captain Hirako had been a delightful surprise.

Based on the data obtained from Captain Hirako, Aizen had successfully completed the "Arrancar" process in Hueco Mundo, transforming Hollows into Shinigami-like beings.

However, his research on "Shinigami Hollowfication" seemed to have hit a bottleneck. Despite arranging the "natural deaths" of nearly a hundred Shinigami over the years, none of them had achieved the desired outcome.