BLEACH : THE NINTH KENPACHI

Though Unohana Retsu agreed to teach Gosuke Shigure Kaidō, it didn't mean she was doing so purely out of altruism.
Aside from the reason Gosuke brought Zaraki to her, she had her own questions for him.
"I wonder... has Captain Gosuke ever heard of Shūsui-ryū Kenjutsu?"
The unexpected question came calmly from Unohana Retsu.
Gosuke Shigure paused when he heard it.
He sighed inwardly.
He hadn't expected anyone to bring up Shūsui-ryū after all these lifetimes. It was truly rare knowledge. But coming from Unohana Retsu, it made sense.
She had lived for centuries, claimed mastery over every known sword style, and likely studied even obscure kenjutsu arts. So it wasn't surprising she knew of Shūsui-ryū.
"Did she notice it during the captain assessment?" Gosuke speculated. Then aloud, he replied, "You're correct. I am indeed a Grandmaster of Shūsui-ryū Kenjutsu. As far as I know, the style is all but extinct now. Very few people still carry its legacy."
"I didn't expect Captain Unohana to recognize it."
Unohana Retsu softly nodded. "As I thought."
"When you underwent your captain's assessment, I noticed something familiar in your swordsmanship. It lingered in my thoughts until I recalled it... a long-forgotten school of kenjutsu—Shūsui-ryū."
"That style faded from history after the death of its founder over a millennium ago. I assumed it had vanished forever. But to see it live on…"
There was a subtle note of nostalgia in her voice.
As for how Shūsui-ryū had survived, Unohana didn't press. She was well aware of its creator's lineage—once a high-ranking noble, respected but ultimately enigmatic. Though his direct bloodline had dwindled, some disciples and admirers clearly took it upon themselves to preserve his teachings.
"To see Shūsui-ryū resurface here in your hands, Captain Gosuke, stirs something within me. It's moving."
She did not inquire further. Now that she understood the source of his unique swordplay, her curiosity was sated.
From that point on, no more questions were asked about it.
For some time after, Gosuke Shigure and Zaraki frequently visited the Fourth Division.
Zaraki studied the foundational skills of Shinigami under Unohana Retsu's supervision—learning about Zanjutsu, Hakuda, Shunpo, and basic Gotei 13 doctrine from one of the Fourth Division's veteran attendants.
To Zaraki, Unohana was the one who had once defeated him. His respect for her ran deep, and because of that, he didn't resist her teachings. While he still disliked formal instruction, he didn't shy away from it either—he gave it honest effort, which, for Zaraki, was rare.
While Unohana tutored Zaraki, Gosuke Shigure focused on learning Kaidō—under the guidance of the Fourth Division's vice-captain.
Although he wasn't taught directly by Unohana, Gosuke didn't mind. What mattered was mastering Kaidō itself.
Kaidō, being a branch of Kidō, shared fundamental techniques and spiritual control with Hadō and Bakudō. The methods used by Unohana and her vice-captain were largely the same—only their effectiveness differed, as Unohana's mastery far exceeded that of her subordinate.
While learning, Gosuke pondered Kaidō's nature.
"Assuming no major disruptions, this vice-captain doesn't have long left in the role," he thought.
In his previous life's memory, Seinosuke Yamada was the Fourth Division's vice-captain about a century ago. But by the time the main storyline began, Isane Kotetsu had succeeded him.
Given the relatively low-risk nature of the Fourth Division, it was unlikely Seinosuke had died in action.
Considering his current age, the most probable explanation was an honorable retirement.
Even while reflecting on this in the back of his mind, Gosuke remained diligent in his Kaidō studies.
As Captain of the Eleventh Division, he still had duties to attend to. He couldn't always immerse himself in training.
Fortunately, Kaidō training was modular. It could be paused and resumed without losing progress.
Though he hoped Zaraki would soon be ready to take on missions and help carry the division's burden, Gosuke ultimately prioritized Zaraki's long-term growth and allowed him to continue training under Unohana.
But the learning process didn't remain peaceful for long.
BOOM!
A thunderous detonation ripped through the air, followed by an eruption of monstrous Reiatsu.
A spiritual storm burst forth, wild and unrestrained. Entire sections of the Fourth Division's buildings were devastated by the force.
The overwhelming Reiatsu spread rapidly across Seireitei, with its epicenter clearly located in the Fourth Division compound. Several captains sensed it immediately.
When Gosuke Shigure arrived on the scene, the Fourth Division's captain's room lay in shambles.
Near the debris, a familiar figure was already present.
"What happened here?"
Gosuke asked the laid-back but alert Kyoraku Shunsui, who stood amid the rubble.
Shunsui adjusted his hat. "Hard to say. I just got here myself. But with this kind of spiritual pressure… I'd guess someone used Bankai right in the middle of Seireitei."
"I see."
Gosuke Shigure's eyes narrowed.
But he knew better.
This wasn't Bankai.
Despite the sheer scale of the Reiatsu—stronger than many Bankai-level pressures—it wasn't the result of a Zanpakutō release.
This Reiatsu was Zaraki's.
And Zaraki… didn't even have a Shikai yet.
Gosuke suspected this was the result of Unohana's instruction—perhaps Zaraki had learned some degree of Reiatsu manipulation, and this eruption was an uncontrolled backlash of that power being tapped for the first time.
Zaraki's innate spiritual power had always been monstrous. If unleashed without restriction, this kind of outburst was entirely plausible.
As Gosuke was deep in thought, Shunsui continued, "Old Man Yama was the first to arrive. He's speaking with Captain Unohana now—probably trying to understand what happened."
"Truth be told, even I was stunned by that flare-up of spiritual pressure."
"If something like that were to happen during a battle in Seireitei, without limits… the damage would be catastrophic."
"Luckily, it happened in the Fourth Division."
He gave a small smile.
"With Captain Unohana here, I doubt things will get out of hand."
To Shunsui, Unohana was one of the most dependable—and dangerous—veterans in the Gotei 13.
He wasn't wrong.