"That was an Observation Killer?!"
As the cloud of woodchips and dust slowly settled, Borsalino slumped against the trunk of a massive tree. In that moment, the usual lecherous grin on his face—half-smirk, half-sneer—had vanished without a trace. What replaced it was a rare expression of solemnity and disbelief.
Observation Killer.
In the world of One Piece, when one masters Observation Haki to the extreme, it becomes possible to suppress one's presence so completely that even the sharpest Observation Haki cannot detect it. This supreme technique is known as the "Observation Killer."
The reason Borsalino had been unable to dodge Yoriichi Tsugikuni's attack boiled down to this: the moment Yoriichi struck, his presence vanished entirely. Borsalino's Observation Haki couldn't even catch a glimpse of his movement.
To a seasoned warrior, losing the ability to sense their opponent's aura is a fatal vulnerability. Had Yoriichi used the blade instead of the hilt just now, Borsalino would be a corpse.
"At such a young age… to have already mastered the Observation Killer technique?"
"Truly unbelievable..."
Borsalino braced his hands against the ground, attempting to stand. But a sharp pain shot through his abdomen, causing his strength to falter, and he slumped back down.
By this time, Yoriichi had already approached, offering a hand with an apologetic expression.
"My apologies, Vice Admiral Borsalino. I just wanted to test a technique I've recently grasped."
"I didn't hold back enough—sorry."
Borsalino stared long and hard at the boy before him, whose face was earnest and filled with regret. After a long silence, he let out a breath, grasped Yoriichi's hand, and allowed himself to be pulled to his feet.
Rubbing his sore midsection where the blow had landed, Borsalino couldn't help but ask:
"How… did you do that?"
Yoriichi understood exactly what Borsalino meant. The ability to completely suppress one's aura—Haki included—was something that could unsettle even the mightiest. It was terrifying in its implications.
But explaining it?
Yoriichi truly didn't know how to explain it to him.
Because his version of the "Observation Killer" wasn't something achieved through pushing Observation Haki to its theoretical limit.
What he used was something else entirely—the State of Selflessness.
In the world he came from, Demon Slayer, when a warrior's technique and perception reached their zenith, they could awaken the power of the "Demon Slayer Mark" and enter the Transparent World.
But even that wasn't the pinnacle.
Above it lay the ultimate state: The State of Selflessness.
The defining trait of this state was the ability to completely "erase" one's fighting spirit. In the terms of this world, that would be akin to nullifying one's "aura" or "killing intent."
Yoriichi had already entered this realm when he first arrived in this world. Back then, he could suppress his aura and killing intent, but not the Haki he had to learn later.
Which was why, during his bouts with Kuzan or Rayleigh, he had been unable to fully conceal his presence—his Haki would always give him away.
But Yoriichi never ceased refining his grasp on the State of Selflessness. As he trained, he explored ways to merge Haki with his breathing techniques, and push the State of Selflessness to greater heights.
Since arriving on this archipelago, his body had grown stronger with each passing day, finally becoming capable of enduring breathing techniques infused with Haki.
From that point on, Yoriichi had dedicated himself to mastering the fusion of the two. And just recently, he succeeded—he could now conceal even his Haki.
The only problem?
There hadn't been any worthy opponents on this island to test it against.
That is, until Borsalino showed up—becoming the perfect subject for Yoriichi's experiment.
And the results were resounding: Borsalino's Observation Haki was rendered completely useless!
Though the effect mirrored that of peak-level Observation Haki suppression, the essence was fundamentally different. The State of Selflessness and the so-called "Observation Killer" of this world were not the same.
Which is why, when Borsalino asked, Yoriichi found himself at a loss for how to explain.
If it couldn't be clearly explained… then perhaps it was best to deflect.
"How I did it... Are you referring to how I hid my presence?"
"I'm not entirely sure myself," Yoriichi replied casually. "I just thought if I could suppress my presence enough to evade my opponent's Observation Haki, it might give me the upper hand in battle… so I gave it a try."
"And once I did, well… it just worked."
"If you're asking why, I honestly don't know."
Yoriichi Tsugikuni answered Borsalino's question offhandedly, his tone as calm as ever.
Hearing that, Borsalino paused—almost as if he'd just been hit by an outrageous humblebrag. He let out a long sigh, shook his head in resignation, and brushed the dust off his cloak and uniform.
His expression slid back into that familiar blend of sleazy nonchalance, the corners of his mouth lifting into a crooked half-smile.
"Man, just thought about it and pulled it off, huh? That's terrifying."
But he didn't press the matter. On this vast sea, the strange and inexplicable were far too common. Encountering a freakishly gifted youth like Yoriichi might be unusual, sure—but hardly unthinkable.
"Not that you'd believe it, but decades ago, there was a five-year-old girl who destroyed an entire Giant village all by herself."
Yes, Yoriichi was a monster in his own right—but even monsters came in categories. He was rare, certainly. But not the rarest. On this ocean, bizarre phenomena were just par for the course.
"Vice Admiral Borsalino," Yoriichi said, gaze unwavering, "Zephyr-sensei must have sent you to assess my strength, right?"
"Shall we continue?"
The blow that had sent Borsalino flying earlier was merely Yoriichi's first experiment with the state of "No-Self". He was eager to fight more—to fully savor the thrill of battle.
But Borsalino raised both hands in surrender, shaking his head firmly.
"Spare me, would you? I've got no interest in continuing this fight."
"You're just too dangerous."
Borsalino wasn't stupid. Now that Yoriichi had grasped the essence of "Observation Killer," engaging in close-quarters combat would make him nothing but a sitting duck. Yoriichi could read him like an open book and control the tempo of the fight entirely.
And if he were to go all out with his Pika Pika no Mi abilities, it would defeat the whole purpose of Zephyr's so-called "trial."
In that case, there was simply no reason to keep fighting.
"Uh…" Yoriichi was a little taken aback by Borsalino's sudden and blatant retreat. He had a rough impression of the man's character, sure—but this level of shamelessness still caught him off guard.
But without a worthy opponent… how was he supposed to measure his growth?
He knew he'd improved—but on this sea of monsters, without testing himself against the truly strong, how could he ever know how far he still had to go before reaching the top?
"Don't worry, Major Yoriichi Tsugikuni," Borsalino said over his shoulder.
"Once we're back, I'll report everything to Zephyr-sensei."
"I'm sure next time, he'll line up someone more… suitable."
"As for me, yeah, I'm not the right guy."
With that, Borsalino turned away, heading straight for the docked battleship without even offering a parting word.
"Well then, farewell, Major Yoriichi Tsugikuni."
With his back to Yoriichi, Borsalino waved casually before disappearing up the gangplank of his warship.
Yoriichi stood at the edge of the pier, watching silently as the battleship raised its anchor and slowly sailed away into the distance. Only then did he exhale lightly, muttering to himself:
"So Borsalino really just came here to take a beating… and then left?"
"I wonder who my opponent will be next time?"
"Surely it won't be another Logia user, right? At my current level, I'd be overwhelmed if they're fully awakened. But if they're not... it'd be over in one move."
"If I were Zephyr-sensei, I'd probably send someone skilled in pure hand-to-hand combat."
"Who could it be...? No way... would he come himself?"
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