Somehow, whether it was thanks to [Chimera's Bloodline Factor] being administered in that brutal 9.5:0.5 ratio, or Vegapunk's five-hundred-years-ahead genius, at the very least—he didn't die.
When it came to transformation waveforms, it was still a double-edged sword, yet he had managed to secure an extremely effective variation.
A provisional form, meant only for islands or nations populated entirely by villains.
In other words—pirate dens, kingdoms of evil.
The so-called "Rampage Form."
Its exact destructive power was unknown. But according to past observations, a reindeer less than one meter tall had exploded into a ten-meter monstrosity in an instant.
Then what if the Nemean Lion, whose beast form already towered at 14 meters at the shoulder, were to go berserk? Even if it grew only tenfold, that would be a colossal body of 140 meters.
An island, even a kingdom, could be annihilated with ease.
He wanted to dig deeper into this newfound ability, but for now, he decided to leave it at that.
Two other vital trainings still awaited him.
Leaving Vegapunk's laboratory, he re-established contact with the Kuja Pirates, and set sail straight for Amazon Lily.
....
"Two Devil Fruit powers… Kyojuro, how is your body holding up?"
Hancock's face went pale when she heard about the bloodline factor aboard the ship, her worry for Rengoku plain as day.
"Mhm! It was an accident, but a blessing in disguise. Whether it's adjusting the size of my hybrid form, or gaining new transformations I'd hoped for—it all turned out well in the end!"
"That's a relief… but just in case, let me at least prepare a nourishing meal for you!"
"Haha! I appreciate the kindness, but I'll pass on a feast with the taste of Devil Fruit itself!"
And so, under Hancock's worried gaze, Rengoku arrived safely at Amazon Lily.
From there, he pitched a tent far outside the village—at a remote edge of the island.
"Kyojuro, why train so far away from the village?"
Hancock was slightly disappointed. She had hoped he might choose her palace as the site of his training.
"Mhm! This training is to evolve the techniques I've been practicing to the next stage! Since you've already mastered Total Concentration Breathing, I was hoping you might join me—if you don't mind, of course. We could even spar together. It would do us both good!"
Rengoku held Hancock in very high regard.
Her talent for breathing reminded him of… Tokito Muichiro, the prodigy who became a Pillar after just two months with a blade in hand.
Already the empress of a warrior's island, already in possession of Conqueror's Haki—her potential was undeniable.
On her very first day she had learned Total Concentration Breathing.
On the second, in Alabasta, she had achieved a state of Upper-Medium stability.
And by now, she was maintaining it with remarkable control. It was time to begin teaching her the forms.
"J-just the two of us?" Hancock asked, almost disbelieving.
"Ah! Does being alone with me make you uncomfortable? If so, I can call San—"
"No, no, no!!! Being just the two of us is perfect! Yes! Only the two of us!"
.....
With its fine defense and flowing continuity—the Water Breathing.
With its sweeping, destructive power in a single stroke—the Flame Breathing.
With its heavy balance of offense and defense—the Stone Breathing.
With its minimum movement yet maximum strikes—the Wind Breathing.
With its speed, swift steps, and iai-like cuts—the Thunder Breathing.
These five were the fundamental Breathing styles of Total Concentration, and Rengoku had trained in all of them during his time with the Demon Slayer Corps.
They had been passed down for a thousand years; Rengoku had studied and mastered their theory and principles long ago.
He could not learn every derivative breathing style unique to other Hashira, but the fundamentals of the five schools—those, he knew inside and out.
He had never forgotten them, even in this new life.
After all, if there was no guarantee the Demon Slayer Corps would not one day fall to demons again, then he needed to remember every ounce of knowledge.
And he had long entertained the idea of merging techniques from other Breathing Styles into his own Flame Breathing.
The mechanics of swordplay were, at their root, the same—thrusting, slashing, deflecting, gouging, twisting strikes.
The differences lay in angles, timing, and the limits of the human body.
Theoretically, the five fundamental Breathing Styles could be fused.
As a former Hashira, Rengoku also knew much about the legendary Sun Breathing.
And so he had formed two hypotheses:
1. Each of the five fundamental Breathing Styles contained fragments of Sun Breathing passed down through generations.
2. By fusing the five, one might recreate—or at least approach—the form of Sun Breathing.
To test this theory, he had chosen this remote site for training.
....
"Kyojuro, everything is ready."
Under Hancock's command, the Kuja Pirates and Amazon Lily's warriors had cleared the beasts from the outskirts, leaving a wide, open space. Wide enough for Rengoku to swing a blade with abandon.
"Much obliged! Then, shall I begin by teaching you a form to match your breathing?"
He set Hancock's training before his own. Her talent could serve as the perfect vessel to test his theory.
Of course, Hancock misunderstood.
Kyojuro is putting my training above his own…? Surely… this must be love! ♥
Ah… Kyojuro, how noble you are…♡
As her imagination ran wild and her cheeks flushed, Rengoku returned with two wooden swords, handing one to Hancock.
"Let's start with Water Breathing. Remember, each style has its own nature, and countless variations are possible. There's no need to feel pressured to copy every movement exactly."
Rengoku raised his bokken into middle guard. Seeing him, Hancock snapped out of her daydreams and took up her stance as well.
"Breathing moves the body naturally, following the form. We'll begin with Water Breathing, First Form: Surface Slash!"
"Understood. Then, I'll rely on you, Kyojuro!"
Meeting her steady gaze filled with determination, Rengoku's lips curved into a smile.
"Then let's begin!"
From Water to Thunder, he guided her step by step through the five schools' forms.
At the same time, he studied once more their essence—through her body.
Every time Hancock performed a form, flawless in execution, Rengoku's eyes sharpened, observing her with laser focus.
The movement of her muscles, the expansion and contraction of her lungs, the intensity of her breaths—
all of it, precise, textbook perfect.
Hancock, however, felt heat rise to her cheeks.
Though she wore her usual clothes, under that piercing gaze it felt as though she stood bare before him.
By the time she had finished every form, from Water Breathing First Form to Thunder Breathing Sixth Form, Rengoku asked:
"Hancock, among all these techniques, which Breathing felt the most natural to your body?"
Hancock paused, thinking seriously, before parting her lips to answer.
"Overall… it felt like every style suited me. I can't really say one was better than the others."
As expected—her talent was extraordinary.
She had affinity with all five styles.
"Then try mixing two of them—any two you like—and attack me!"
Rengoku lifted his wooden sword, ready to receive her strike.
Hancock stepped forward, blending Flame Breathing with Thunder Breathing in her slash.
Clang!
It carried both the force of flame and the speed of lightning, yet… something was missing.
"Instead of forcing it, why not use them the way you did your Total Concentration—let your breath flow naturally, weaving them together as instinct guides you?"
Unlike Rengoku, who had fully mastered Flame Breathing, Hancock was still a novice in each of the others.
But that was an advantage—she had no ingrained habits to restrict her.
And so she attacked again.
This time, it was different.
A gifted warrior learning many techniques at once, leaving her body to instinct—that was Hancock now.
Sometimes her strikes carried the fluid connection of Water and the bold power of Flame.
Other times they held the heavy solidity of Stone and the speed of Thunder.
Her offense sharpened with every blow.
Rengoku parried each one, Observation Haki at full strength, studying her every breath.
At times she blended two styles.
At times three.
At her peak—four: Water, Flame, Stone, and Thunder.
Unlike Rengoku's Flame-centered fusion, Hancock's style had no anchor—it was raw, instinctive, chaotic yet alive.
"More! Push harder, Hancock!"
"Understood!"
Her strikes grew fiercer under his command.
Her breaths—inhale, exhale, sharp, steady—each carried the mixed tones of the five schools.
Rengoku mimicked her rhythm.
His Flame-based core now layered with four other styles.
Had it been only his own training, it might have taken him far longer to grasp.
But with Hancock as a living example, the essence came quickly.
It was the first time since learning Total Concentration Breathing that Rengoku had imitated another's breathing.
And it was fresh, powerful—undeniable in its effect.
Dozens of exchanges passed. Hancock's stamina began to waver.
"Hahh… hahh…"
Sweat beaded across her brow.
But for Rengoku, the data he needed was complete.
"Hancock, put down the sword. Now, attack me in your way."
Her true strength was in her legs—those elegant, long kicks, dazzling and deadly.
Seeing her, now seasoned in blending the five breaths, Rengoku felt his own excitement stir.
On one side: his own Flame-centered fusion layered with four others.
On the other: Hancock's instinct-born, naturally woven fusion of all five.
Two new breaths, born in parallel—alike, yet entirely different.
It was the moment Fusion Breathing truly began.
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