Afterwards, it took half a month for Toshiro to fully master Hado #90, Kurohitsugi. Then, it took about another half month to be able to perform it without incantation.
Although it only took about a month total to achieve incantationless casting of Hado #90, which was incredibly impressive, and no one had been heard of doing it faster than Toshiro, compared to Toshiro's previous learning speed, it was nothing.
Back at the Shin'o Academy, low-level Kido could be performed just by looking at the method. Intermediate Kido could be mastered after one practice. Even high-level Kido below the 90th only required a bit of effort and a few more practices.
Spending a whole month specifically practicing one Kido was a first.
Of course, in terms of power, Kido above the 90th and below were completely different, like heaven and earth.
Kido below the 90th could hardly pose a fatal threat to Captain-level powerhouses. But for Kido above the 90th, even Captain-level powerhouses would be severely injured or killed if hit.
In the original work, Aizen's incantationless Kurohitsugi had only one-third normal power, yet it instantly defeated Komamura.
Nighttime, in a training room of the 10th Division.
After handling the 10th Division's work, Toshiro didn't return to his residence to rest. Instead, he stayed directly in the 10th Division's training room.
Toshiro sat cross-legged on the floor, placing his Zanpakuto on his legs.
However, Toshiro wasn't communicating with his Zanpakuto or training his Reiatsu. He closed his eyes, focusing inward to observe his body's internal state.
Of course, ordinary Shinigami couldn't perform internal observation. Toshiro was currently using his [Dragon's True Eye] ability to observe his inner world from within.
[Dragon's True Eye] could see through falsehoods and perceive everything, but it could also be used to observe one's own condition.
Over the years, as Toshiro's strength increased and he frequently practiced using the ability, the duration for which he could use the [Dragon's True Eye] had greatly extended.
Toshiro once tested it, and even after ten consecutive hours, he hadn't reached the limit and could maintain it further.
When Toshiro activated the [Dragon's True Eye] and calmly observed his Inner World, he saw his internal organs like the heart, liver, spleen, and lungs suddenly transform into countless tiny Reishi particles.
But Toshiro wasn't surprised, as this was expected.
A Shinigami's body was composed of Reishi, not true flesh and blood. This was the real difference between Shinigami and humans.
Shinigami and humans looked completely alike in appearance but were classified as different species, primarily because of this.
It's just that the Reishi composing a Shinigami's body were too tiny. Even if ordinary Shinigami had internal observation abilities, they could only see the body organs composed of Reishi, not the individual particles.
Toshiro could see them because he relied on the Dragon's True Eye ability.
Under the Dragon's True Eye, Toshiro's body appeared as countless Reishi particles, arranged in an orderly human form.
The Reishi particles composing Toshiro's body weren't completely fused together, and there were gaps between them.
Seeing this, Toshiro carefully used his Reiryoku to control the Reishi particles, making them press together and reduce the gaps between them, even making them disappear entirely.
Toshiro did this mainly to compress the density of the Reishi composing his body.
The smaller the gaps between Reishi particles, the higher the body's Reishi density, and consequently, the stronger the body's physical strength.
Under the Dragon's True Eye, Toshiro could fully understand every part of his body's condition and compress and enhance it as needed.
If this continued, Toshiro's body would become terrifyingly strong. Enemies might not even be able to break his physical defense, let alone injure him.
Increased body strength wouldn't only boost Toshiro's defense but also help him further master Hyorinmaru's power.
Because Hyorinmaru's power was too great, Toshiro's Bankai at the Captain-level was immature, with various limitations.
Although since breaking through to mid-stage beyond Captain-level, Toshiro had mastered mature Bankai and could unleash Hyorinmaru's true power, it was still a strain.
Previously, when using true Bankai, Toshiro's body would rapidly grow to adapt to the power… the so-called 'aging' side effect.
Although Toshiro was quite satisfied with becoming a handsome adult after 'aging', this state put severe strain on his body, preventing him from maintaining Bankai for long. In such a case, if a battle couldn't be ended quickly and turned into a drawn-out fight, it would be extremely disadvantageous for Toshiro.
This side effect ultimately stemmed from Toshiro's body not being strong enough to fully bear Bankai's power.
So, the stronger Toshiro's physical constitution, the longer he could maintain Bankai. This would greatly help Toshiro unleash Hyorinmaru's true power.
Toshiro trained in the training room all night until the next morning when 10th Division's members started getting up for work. Only then did Toshiro end his training and stand up.
"Aah—"
Toshiro couldn't help but yawn.
"Morning already? So fast," Toshiro murmured to himself.
Engrossed in training, Toshiro didn't notice time passing until the commotion of members moving around outside woke him.
Then, Toshiro walked to the training room's weapon rack and took out a sharp katana.
Shiing!
Toshiro drew the katana from its scabbard. Looking at the blade's cold gleam, Toshiro nodded in satisfaction, then gripped it with his right hand and slashed fiercely at his left arm.
Clink!
A crisp sound rang. Toshiro's arm was completely unharmed. Instead, the katana in his right hand broke into two pieces.
"Hmm, seems my body's strength is pretty good," Toshiro said contentedly.
Although it was a katana, not a Zanpakuto, in terms of sharpness alone, it wasn't much inferior. Moreover, Toshiro had infused the blade with Reiatsu no less than Lieutenant-level. This showed how strong Toshiro's physical constitution had become.
Of course, this wasn't achieved overnight. Compressing his body's Reishi density and increasing physical strength were things Toshiro had started long ago.
After testing his body's strength, Toshiro left the training room, ready to start a new day.