The principle of Zanpakuto's release is somewhat similar to the Gikon invented by Hikifune Kirio of the 12th Division.
In fact, the Gikon created by Kirio was developed based on the Reiatsu changes that occur during Zanpakuto's release. In the Bleach World, the name is power!
The soul is the source of power.
However, an individual's soul has its limits.
To obtain greater power, countless predecessors devoted themselves to researching the soul.
Eventually, researchers discovered that if an individual's soul has limits, they could fuse other souls with their own to break through those limits and reach a higher realm.
The Zanpakuto was created by Nimaiya Oetsu.
The prototype of the Zanpakuto originated from the souls of Gillian-class and higher Hollows. Oetsu refined them back to their original form, forging them into Asauchi.
These Asauchi are then nurtured by the Shinigami's own soul, forming a deep bond with them. When the frequencies of the two souls align to a certain degree, communication becomes possible, allowing the Shinigami to learn the Zanpakuto's name and achieve a temporary soul fusion.
This is why, after releasing their Zanpakuto, a Shinigami's Reiatsu increases by three to five times.
Bankai, on the other hand, is a deeper fusion between the Shinigami and the Zanpakuto's Spirit, resulting in a five to tenfold increase in Reiatsu.
However, while the emergence of Zanpakuto marked a major step forward in the power of Shinigami, the fusion between a Shinigami's soul and the Zanpakuto's Spirit is only temporary and requires the Shinigami to possess a certain level of Reiryoku.
Whether it's Shikai or Bankai, unless the Zanpakuto's ability is special, releasing it will continuously drain the Shinigami's Reiatsu. Once the Shinigami's Reiatsu falls below a certain threshold, the two fused souls will separate again, manifesting as the Shinigami being forced to deactivate their Zanpakuto release.
Regardless, Zanpakuto release is the first major hurdle for Shinigami.
Those who cross it can become seated officers in any division, placing them among the upper echelons of Shinigami.
Thus, both Kyoya and Gin Ichimaru were very concerned about Matsumoto Rangiku's training progress.
"Mmm, I heard it."
Rangiku smiled gently and stroked the Zanpakuto at her waist.
"This child says her name is Haineko."
"Haineko?"
Kyoya and Gin were overjoyed.
The fact that Rangiku now knew her Zanpakuto's name meant she had crossed the chasm between an ordinary Shinigami and a seated officer.
At the same time, upon hearing the name [Haineko], Gin lowered his head slightly in thought.
He felt that the 'ash' in [Ash Cat] had some connection to him. (T/N: Haineko means Ash Cat.)
Then, Gin remembered that Rangiku's soul had been missing something important, taken by Aizen, and it was his own soul that had filled that gap, allowing Rangiku to survive.
Clearly, the 'ash' in [Ash Cat] might represent the essence of his soul.
Rangiku is the 'cat'.
At this thought, Gin Ichimaru raised his head and glanced at Rangiku, nodding slightly.
'Yes, Rangiku is indeed a cat!'
'A persian cat!'
As for Kyoya, he already knew Rangiku's Zanpakuto was Haineko, and he also knew that the 'ash' in [Ash Cat] referred to the 'ash' in Gin's Shikai, Shinso.
"Rangiku, do you want to give it a try?"
Seeing Rangiku's expression, Kyoya raised an eyebrow.
"Um..."
Rangiku had a conflicted expression on her face.
Indeed, having just learned the name of her Zanpakuto, she also wanted to test out its abilities.
But if she were to fight Kyoya, she'd probably end up crying, wouldn't she?
Back when she was a kid, crying wasn't a big deal, and she'd even get sympathy from everyone, and they'd all scold Kyoya together.
But now that she was all grown up, if she got beaten so badly she cried, not only would she not get any sympathy, she'd probably be laughed at for a long time, right?
"Don't worry."
Just one look at Rangiku's face, and Kyoya already knew what she was thinking.
Rolling his eyes, Kyoya reassured her, "I won't hit you. I just want to test out your Zanpakuto's abilities."
"You promise?"
Hearing this, Rangiku immediately brightened up.
"Alright, Gin, you be the referee for us! If Kyoya dares to hit me, you step in and help me beat him up!"
"Fufufu, sure."
There was no way Gin would refuse Rangiku's request.
Even if he knew that stepping in wouldn't actually stop Kyoya, he'd still do it without hesitation.
Seeing that Kyoya and Rangiku were about to spar, everyone else in the training ground quickly wrapped up their own battles or training, silently clearing out space for the two.
Standing opposite Kyoya, Rangiku took a deep breath and drew the Zanpakuto at her waist.
Then, she pressed her left hand against her Zanpakuto's blade and softly chanted-
"Growl, Haineko!"
Boom!
This was her first time releasing her Zanpakuto, and Rangiku wasn't yet skilled at controlling the sudden surge in Reiatsu, so the excess energy flickered around her body like flames.
Meanwhile, her Zanpakuto transformed into countless fine particles of dust.
At first, they were clustered together, still visible to the naked eye. But as Rangiku willed them to disperse, they became nearly invisible… only detectable through Reikaku. The area around her was now filled with countless tiny points of Reishi.
After releasing her Zanpakuto and briefly familiarizing herself with its abilities, Rangiku narrowed her eyes and smirked.
"Kyoya, my Zanpakuto's ability is to turn into dust. These particles can be controlled by my will, and then…"
Whoosh, whoosh, whoosh-
A fierce gust of wind swept through as the dust surged toward Kyoya.
Just as it reached him, Rangiku swung the hilt of her Zanpakuto downward-
Clangclangclangclang-
In an instant, countless sparks erupted around Kyoya.
It was as though hundreds, or even thousands of blades were slashing at him simultaneously.
"Not bad, huh?"
"This is Haineko's power!"
Raising the hilt of her Zanpakuto triumphantly, Rangiku declared, "Whenever I swing this hilt, every single particle of dust acts like a blade, cutting at the same time!"
Then, with a thought, the swirling dust around her condensed into a solid barrier, "And these particles can also form a defensive wall with pretty decent durability."
"Mmm, an excellent Zanpakuto."
Kyoya nodded in approval.
Then, he took a few steps forward, raised his right hand, and flicked his fingers against the dust barrier in front of Rangiku-
Bang!
In an instant, the wall of dust was shattered, leaving a gaping hole and revealing Rangiku's confused look behind it.
"Cough-"
Seeing this, Kyoya coughed lightly into his hand, pretending to clear his throat: "Well, of course, it's not without its weaknesses."
He hadn't expected the defense crafted by Haineko to be so fragile that a single flick would break it.
'Hopefully, this wouldn't crush Rangiku's confidence…'
"Both its offense and defense are just average."
"For regular Shinigami, it's a solid ability."
"But it's still too weak against the Captains."
"Also, Rangiku, you should test whether the amount of dust your Zanpakuto turns into is fixed or if it increases along with your Reiatsu."
This would determine Rangiku's potential.
If the amount of dust increased with her Reiatsu, then she might be able to train using a similar approach to Byakuya's.
While Haineko's offensive power and numbers couldn't compare to Senbonzakura, it had its own advantages.
Every time Rangiku swung her hilt, the dust would act as blades, as though the particles and the hilt were connected regardless of distance.
If, in the future, Rangiku became a Great Swordsman capable of launching flying slashes, then Haineko's dust would essentially become countless invisible blades for her ranged attacks.
At that point, even if she hadn't reached 3rd-class Captain-level Reiryoku, she'd likely possess strength comparable to an average Captain.
Wouldn't that be way stronger than the Rangiku from Kyoya's memories?
Of course, right now, she was still far from reaching that level.
"How could it be that I'm weak? It's just that you're way too strong!"
Rangiku puffed out her cheeks and shot Kyoya an exasperated glare.
The members of the 11th Division nearby all nodded in agreement.
Seriously, what she said is spot on.
Hadn't they all seen the countless sparks flying off Kyoya's body when Rangiku swung her hilt?
For them, that kind of reaction only happened when their Zanpakuto struck an opponent of equal strength's Zanpakuto with all their might.
In other words, those sparks meant that Rangiku had effectively landed hundreds, if not thousands, of full-power slashes on Kyoya.
And yet, not a single one had broken through his defense.
Back in the day, they could still somewhat gauge Kyoya's strength.
But at some point, their Zanpakuto couldn't even scratch him anymore. It was downright despair-inducing.
Honestly, only a 'monster' like Kyoya could casually flick his fingers and shatter Haineko's defense like that.
If it were any of them, they'd probably be helpless against Rangiku.
Though she'd retorted, Rangiku still took Kyoya's words to heart.
After testing whether she could channel more Reiatsu into the hilt, faint wisps of gray mist began seeping from it.
"Good."
Seeing this, Kyoya nodded in satisfaction, "It seems like the amount of dust your Zanpakuto produces is directly tied to your Reiatsu."