Yachiru Unohana  

"I am Ailin Kenpachi, Captain of the 11th Division of the Gotei 13."

"Captain Ailin, I am Gin Ichimaru, a student who graduated from the Shin'ō Academy this year." Gin Ichimaru bowed his head and introduced himself to Ailin for the first time.

"Is that little girl okay now?"

"Yes, thanks to Captain Ailin, Rangiku woke up without any discomfort. Please allow me to express my gratitude to you once again, Captain Ailin."

"Protecting the residents of the Rukongai from harm is the responsibility of the 11th Division. However, the Hollows are easy to kill, but those rats hiding in the shadows rarely show themselves.

Moreover, those fellows have strong concealment abilities. Over the past three years, although I have discovered the identity of the Shinigami I killed, I have no clue about the identity of the one who escaped. Gin, I'm glad you listened to my words and truly joined the 11th Division.

This world harbors many unknown dangers that may suddenly befall us or those we care about without our awareness. At such times, we must possess the power to confront these dangers in order to protect what we cherish."

"Yes, you're right, Captain Ailin."

"As I mentioned before, if you became a Shinigami and joined the 11th Division, I would personally train you. If you have another residence in the Seireitei, we can start your training now.

If you don't have a residence, go find 3rd Seat Gosuke first and have him familiarize you with the 11th Division's barracks and dining hall. We'll start your training tomorrow. Is that okay?"

"Yes, I understand, Captain Ailin."

"Then I'll go find the 3rd Seat now."

"Go ahead."

***

In the 4th Division, Retsu Unohana narrowed her eyes, holding a cup of tea and slowly savoring it.

Thump, thump, thump...

Suddenly, hurried footsteps echoed in the hallway, and a flustered white-haired girl rushed into Captain Unohana's meeting room.

"Captain Unohana, Captain Unohana, I've inquired about the matter you asked me to investigate from a member of the 11th Division."

This young girl sounded underage, but her legs were disproportionately long, making her taller than her age would suggest.

"Isane, as a medical professional, you must maintain emotional stability. It will greatly aid you in using Kidō for patient treatment."

"Yes, Captain Unohana."

As Retsu Unohana set down her teacup, a hint of disappointment flashed across her mind. Compared to her former lieutenant, Seinosuke Yamada, Isane Kotetsu, this young girl fell short.

However, Isane had decent talent, excelling in both Konsō and Kidō. As her spiritual pressure increased, her strength would steadily improve.

After Isane Kotetsu left the 4th Division, Retsu Unohana began mentoring her as her deputy.

"Tell me, what did you learn from that member of the 11th Division?"

"Yes."

After composing herself, Isane Kotetsu reported to Unohana, "Captain Unohana, that member said their captain has recently taken on a genius Shinigami as a disciple and has been teaching the disciple in Rukongai district."

"Rukongai, huh? That's a familiar place..." Unohana mused inwardly.

Over a thousand years ago, Retsu Unohana was once a great evil in the Soul Society, mastering all the sword styles of the Soul Society and calling herself the "Eight Thousand Flows"

Even after being defeated by Genryūsai Shigekuni Yamamoto and becoming the first Kenpachi of the Gotei 13, Unohana's desire for slaughter was never suppressed.

Unable to engage in battles within the Seireitei, she often ventured into the Rukongai to seek out strong opponents for combat. Back then, the sword masters she slew could have formed a mountain.

Until one day, Retsu Unohana, the Eight Thousand Flows Master, encountered a youth who shared her desire for slaughter...

Recalling that youth, Unohana unconsciously touched her chest. Beneath her long braid, hidden from view, was an unsightly scar. This scar constantly reminded Unohana, the first Kenpachi, that she had lost the title of "Strongest Shinigami" in that battle. Moreover, it was in an extremely humiliating manner.

It was precisely because of her realization of her own weakness that Retsu Unohana established the rule of "responding to challenges with all her might."

The seventh generation Kenpachi, Kuruyashiki Kenpachi, once apologized to the eight Kenpachi challenger, Sōya Azashiro, for not wanting his subordinates nearby to die at his hands, as he did not show Sōya his full Bankai.

Over the years, Unohana had refined her Kidō and combined the ability to transform her spiritual pressure into healing hot springs, learned from Tenjirō Kirinji, with the power of her Zanpakutō.

She was confident that if she encountered that youth again, she would never allow her weakness to force him to lower his spiritual pressure to accommodate her.

However...

The first time she sensed a sword style completely different from her mastery of all sword styles in the Soul Society emanating from Captain Ailin of the 6th Division, Unohana's desire for battle nearly overwhelmed her.

Never underestimate the anticipation of someone who has mastered all the sword styles of the Soul Society when encountering a new sword style.

Especially after learning from the Kuchiki family's lady that Ailin's spiritual pressure had reached a certain level, Unohana almost drew her sword to fight Ailin at that moment.

So, when Sōya Azashiro turned himself in and was imprisoned in the Muken, leaving the position of 11th Division Captain vacant, Unohana suggested Ailin's name.

Each era could only have one "Kenpachi!" This was her destiny!

Feeling the overwhelming desire within her, Unohana's gaze suddenly became lifeless. It was as if the former great evil was about to tear through her hypocritical shell and immediately rush to the Rukongai to engage Ailin Kenpachi in battle.

"Cap-Captain Unohana." A terrified voice snapped Unohana out of her reverie of past slaughter.

Narrowing her eyes, Unohana realized she had seemingly frightened the young girl before her.

"Ah, my apologies, Isane. I was just recalling something. Did you notice anything unusual?" Gently patting Isane Kotetsu's hair, Unohana softly reassured her.

"No, I must have been seeing things." Comforted by Unohana, Isane basked in the captain's warmth.

After all, Captain Unohana was the idol of all female Shinigami in the Seireitei – beautiful, gentle, and incredibly powerful... The gentle and virtuous Captain Unohana could never have such a terrifying gaze.

"Rukongai, huh?"

After Isane Kotetsu left, Unohana took out a piece of paper and began writing her final words.

"Isane, by the time you read this letter, I will have..."

As the sky darkened, Unohana sealed the letter, its ink now dry, and placed it on her desk in the captain's quarters.

If she returned, she would destroy this letter. But if she did not come back tonight, Isane Kotetsu would naturally find the letter tomorrow and deliver it to the Captain-Commander.

Glancing up at the moon in the sky. "The moonlight is truly beautiful tonight..."

Beneath the serene moonlight, Unohana undid her hair tie, allowing her braided bun to unfurl and sway in the night breeze.

"A perfect night for battle..."

A chilling, lifeless voice escaped Unohana's lips. In the next moment, her figure turned into an afterimage, rushing towards Rukongai...

***

In Rukongai.

A slender figure was engaged in battle with a few Hollows. Or rather, it was not a battle, but the Hollows attacking while the youth evaded.

Near the battlefield, Ailin stood with his arms folded, observing Gin Ichimaru's performance. Indeed, in Ailin's eyes, Gin Ichimaru's fight against these three Hollows was a mere "performance."

With his eyes closed, Gin could sense the Hollows' movements before they attacked and evade them with minimal movement.

If observed more closely, or by a powerful Shinigami, an even more terrifying sight could be witnessed.

Each of Gin's evasions positioned him in the optimal spot to instantly kill the Hollows with his fastest strike.

"Not bad."

Satisfied with Gin's performance, Ailin nodded in approval.

Knowing Gin's target, Ailin focused on training Gin's "sensory" abilities during their sessions.

The Observation Haki! This was a powerful ability to sense an opponent's movements, predict their actions, and even foresee the future at its highest level of mastery.

Of course, since the versions differed, Ailin could not provide Gin with the "Pirate" series weapons he had forged, so Gin could never truly cultivate the Observation Haki.

However, in the world of Shinigami, battles were fought through sensing an opponent's spiritual pressure and movements.

Sōsuke Aizen's "Kyōka Suigetsu" could control an enemy's five senses, achieving "complete hypnosis." But as long as one touched Kyōka Suigetsu's blade before Aizen released his Zanpakutō, they would not be affected by its abilities.

Bakudō #58 Kakushitsuijaku and Bakudō #77 Tenteikūra, the sensory binding spells, could detect Sōsuke Aizen's spiritual pressure.

Ailin taught Gin a version of "Observation Haki" he created based on these two Bakudō spells.

When employing this Shinigami version of "Observation Haki," one's spiritual power would expand outward like the sensory Bakudō, merging with the surrounding spirit particles. Through the fluctuations of these particles, one could sense the enemy's movements.

To a certain extent, this created a "sensory barrier" around oneself.