One Piece: Start with Zanpakutō

A flash of purple light.

Centered on Rosen himself, a semicircular shield burst forth, spreading in all directions. Black and red lightning snaked across its surface, like a black dragon coiling protectively, standing firm against Brynndi World's hundredfold stomp with an indestructible posture.

Boom!!

Brynndi World's massive foot crashed down upon the outer shell of the Blut Vene Anhaben. At once, an overwhelming shockwave exploded outward, shaking even Impel Down Beneath the sea so fiercely that it seemed the entire prison might be uprooted.

However—

Despite enduring such a direct, monstrous attack, Rosen's Blut Vene Anhaben only vibrated violently; not a single crack appeared on its surface. On the contrary, as Brynndi World's Armament Haki-clad foot met the suit, his domineering aura instantly dissipated, his hardening undone, leaving only bare skin.

That wasn't the end.

On the surface of the Blut Vene Anhaben, streaks of purple light suddenly slithered out like spirit snakes. Some burrowed into his flesh, transforming into strange tattoo-like lines that rapidly spread across the surface of his skin.

Others crept up along his leg, directly penetrating the deep chest wound that exposed even his bone, and flooded into his inner organs.

"AAAHHH!!!"

Brynndi World, intending to raise his foot again and hack downward with his left leg like a giant black axe, suddenly felt an uncontrollable swelling sensation explode inside his body.

This was followed by a heart-wrenching pain.

Pshhh—

In an instant, his entire skin turned bright red and bloated. Then, his nostrils, eyes, ears, and mouth simultaneously began gushing blood like fountains.

Especially from the chest wound Rosen had opened earlier — blood surged forth as if dozens of crushed tomatoes had burst inside him, spraying out like a fountain onto Rosen's Blut Vene Anhaben, dyeing the semicircular shield bright scarlet.

Crack—

Brynndi World's eyes rolled backward. His once-giant body shrank rapidly back to human size. Then, with a dull thud, he fell heavily from midair and collapsed at Rosen's feet.

Blood continued to spurt from every pore of his body, rapidly pooling into a sticky, crimson lake on the ground.

"Wh-What… is this?"

Among everyone present, the one who reacted most intensely was none other than Domino.

The Blut Vene Anhaben — she still remembered vividly that Rosen had used this technique to help her resist the freezing air on the Fifth floor of Extreme Cold Hell.

But now…

The same technique had just killed the World Destroyer on the spot.

"I see it now."

"Applying the Blut Vene (Calm Blood Dress) to the enemy instead?"

"Combining Emission, internal destruction, and the Blut Vene Anhaben, creating an external shell that, once in contact with the enemy, not only defends but allows Rosen's Armament Haki to invade the opponent's body, corroding flesh, flowing into their blood vessels, and wreaking havoc from within…"

A flash of profound understanding appeared in Zephyr's eyes.

As Rosen's teacher, and the one most familiar with his abilities, Zephyr instantly grasped the cause of Brynndi World's death at a glance.

And he marveled at Rosen's delicate, terrifying mastery over his Haki.

If it were someone else, even Zephyr himself or the Garp, they could only inject Armament Haki to damage an opponent's organs in a rough, explosive manner.

But to do what Rosen did — to precisely guide the Haki into the blood vessels and destroy the enemy from within, like a hidden venomous blade — was unimaginable.

Neither Zephyr, nor Garp, nor even any Marine Headquarters figure could achieve it.

"In terms of control over Armament Haki techniques alone, he's completely surpassed me… no, surpassed everyone in Marine Headquarters."

Looking at Rosen's back, Zephyr couldn't help but show a deeply relieved, almost fatherly smile.

This was what he had devoted his final years to nurturing new talents.

As a teacher, what could be more gratifying than seeing one's own student surpass oneself?

"How did he… manage this?"

Shiryu's eyes were filled with shock and confusion.

"Junior…"

"You really are a monster beyond reason."

Borsalino shook his head slowly.

During the entire battle between Rosen and Brynndi World, Borsalino had nearly intervened several times.

After all, Rosen had only begun learning Haki three days ago. Even if Brynndi World's personal combat strength wasn't particularly overwhelming, he still possessed the terrifying More-More Fruit — a threat that could never be underestimated.

Yet, to his astonishment, Rosen not only defeated Brynndi World alone, he also completely controlled the fight's tempo from start to finish.

In the end, aside from a few drops of blood on his clothes, Rosen emerged completely unscathed.

"He… he's dead?"

"He really killed Brynndi World…"

"That brat… he can use Conqueror's Haki Infusion!"

"Damn it… it's one thing for the navy to have someone with a Conqueror's Haki… but to think he can already use advanced Conqueror's Haki techniques at that level!"

The prisoners on the sixth floor, who had witnessed Rosen slaughtering Brynndi World, were all frozen in shock.

They weren't just stunned by Rosen's raw power — it was the terrifying array of techniques he displayed.

Beyond his absurdly refined Armament Haki techniques…

There was also the Infusion of the Conqueror's Haki — a symbol of true kingship.

And it had appeared in a "student" who hadn't even graduated from Marine Academy.

"World Destroyer…?"

Rosen lowered his Blut Vene Anhaben, ignoring the prisoners' horrified exclamations.

Instead, he cast a cold glance at Brynndi World, now lying lifeless at his feet, body shredded, blood vessels burst, no longer showing even the slightest sign of life.

"Take it away."

"Next one."

He casually signaled Domino to come forward and clear away Brynndi World's corpse, and then to bring out the next prisoner.

It was no wonder Rosen was so proactive.

In this battle with Brynndi World, aside from not fully unleashing the potential of his Arms-Arms Fruit, he had used all Three Forms of Haki to the limit, along with every technique he had learned and developed.

Not only was the fight exhilarating to the extreme, but it also greatly enhanced the strength of all Three Forms of Haki.

[Your comprehension is extraordinary. Through the battle with Brynndi World and Refinement of the Haki Core Origin, your Three Forms of Haki have reached a breakthrough level.]

[Armament Haki strength increased by 225%.]

[Observation Haki strength increased by 183%.]

[Conqueror's Haki strength increased by 110%.]

All Three Forms of Haki had undergone explosive growth. Even the "smallest" increase, Conqueror's Haki, had more than doubled.

Observation Haki nearly doubled outright.

And Armament Haki — the most frequently used throughout this battle, from beginning to end — had been refined and strengthened to an even greater extent, nearly tripling.

In addition to these visible improvements, there were also hidden Benefits.

His Haki Core expanded, and his Refinement speed for all three Haki colors had further accelerated.

"The stronger my opponent's Haki, the more extreme the improvement, huh…"

Rosen recalled the previous Conqueror's Haki clash with Douglas Bullet.

Even though they hadn't actually exchanged blows, the sheer strength of Douglas Bullet's Conqueror's Haki had given him an over two-fold increase just from a single, fierce clash.

Whereas with Brynndi World, though it was a real life-or-death fight, the greatest improvement still didn't surpass the gains from clashing with Douglas Bullet's overwhelming spirit.

Rosen wasn't surprised.

The stronger the opponent, the greater the risk.

If the gap in Haki was too vast, before you could even grow stronger, you would be crushed to death on the spot.

Why was Douglas Bullet able to possess Yonko-level combat power before the age of twenty?

Innate talent was certainly a prerequisite.

Yet, on this ocean, there were countless people with just as monstrous talent, if not even more so.

The true reason was that Douglas Bullet constantly fought against Roger, Rayleigh, Jabba, and the other kings aboard Roger's ship day and night.

Even if he lost repeatedly, they wouldn't kill him — at most, they would beat him within an inch of his life.

But precisely through that endless cycle of defeat and combat, Bullet forged himself.

In the end, even without mastering Haki Core Origin or the Rokugan Rebirth (Six-Organ Rebirth), he still grew into an emperor-level monster through countless battles with the kings of Roger's era.

...

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