The days Tomioka Giyu spent at the training hall were sliced into precise fragments of discipline.
Before dawn, when the roar of the waterfall still carried the chill of night, he was already standing beneath it, letting the freezing torrent crash against his body.
The water pounded his shoulders and back with a force that would have broken most people in minutes, but he simply closed his eyes and adjusted his breathing, syncing the rhythm of Water Breathing with the pulse of the current.
It was Urokodaki Sakonji's own method—one meant to temper both willpower and body, making one's breathing flow as naturally as water itself.
In his past life, Giyu had endured countless days and nights under this very waterfall, unable to hold his stance for more than three hours until his body finally adapted.
Now, after only half a month, he could stand there for four hours with ease.
Not because this younger body was stronger—but because his mastery of breathing was now precise to an inhuman degree.
Each inhale timed to avoid the waterfall's heaviest strike,
each exhale distributing strength evenly across his muscles, perfectly offsetting the pressure of the falling water.
When daylight came, it was time for sword practice.
On the clearing in front of the house, the wooden training posts were shredded from endless slashes, jagged stumps marking every cut.
Giyu gripped a wooden blade, repeating the basic Water Breathing forms over and over.
For the First Form, Water Surface Slash, he practiced the stance thousands of times a day—
the angle of his wrist, the speed of each swing, the shift of his center of gravity—every movement broken down, polished, rebuilt until his muscles moved with unerring precision.
Urokodaki sometimes stood beneath the eaves, silent, the tengu mask hiding his expression. But Giyu could still feel that watchful gaze on his back.
Once, when he was practicing the Seventh Form, Drop Ripple Thrust, the old man suddenly spoke.
"Lower your wrist by half an inch. Exhale sharper on the thrust."
Giyu immediately adjusted his motion—and the moment he did, he felt the blade's penetration power increase noticeably.
He still hadn't completely synchronized with this younger body. For now, he relied on fragments of old experience to rebuild new muscle memory, correcting every unfamiliar motion bit by bit.
Without turning, he said quietly, "Thank you, Sensei."
"Your progress is too fast," Urokodaki's muffled voice came from behind the mask, laced with a faint, complicated emotion. "But don't rush. The stronger the foundation, the steadier your future steps."
"Yes."
Giyu understood his teacher's meaning.
His feat of slaying a Lower Moon had been shocking, but he knew the truth—that demon had likely been one of the weakest, perhaps newly promoted, not yet in full control of its Blood Demon Art.
If he faced a stronger Lower Moon—or an Upper Moon—his current strength would still fall short.
He needed to grow stronger.
Not only perfect the existing Water Breathing forms—but create something beyond them.
Afternoon sunlight filtered through the trees, scattering across the ground in a patchwork of gold.
Giyu sat on a wooden post, carefully wiping the blade of his Nichirin Sword.
The steel reflected his face—young, but calm to the point of stillness.
His thoughts drifted to the battle in the Infinity Castle from his past life—when he faced Akaza, Upper Moon Three.
The demon's fists had moved so fast that Water Breathing itself had felt powerless before them.
He rose and took the stance once more, gripping his sword firmly.
Inhaling deeply, he let the rhythm of Water Breathing surge through his body.
He didn't strike immediately. Instead, he closed his eyes, imagining the flow of water around him—
not a raging waterfall, nor crashing waves, but calm, seamless currents looping endlessly like a great circle, a fluid shield that redirected every attack away.
Such a form required absolute control.
It wasn't just about breathing. Every muscle had to respond in perfect harmony, the exhaled breath forming invisible spirals of air that guided the blade's circular path.
Giyu opened his eyes, the blade moving in a smooth arc.
"Fwoom—"
The air itself split open, shimmering with faint blue ripples.
But instead of extending forward, the water trace before him formed an incomplete ring—then vanished.
Failure.
He exhaled slowly. It was the body's unfamiliarity, not the technique.
No discouragement. Only adjustment.
He took the stance again.
Once.
Twice.
Three times.
The hum of the Nichirin Sword echoed through the clearing, each stroke faster than the last.
The watery arcs grew sharper, the traces more defined.
Sweat streamed down his temples, dripping onto the hilt. He wiped it away without noticing, his entire focus narrowed to the single vision of that circling current—
and the invisible pattern of his breath within it.
This was where his sharpened sword talent truly shone.
Each time he failed, he instantly located the flaw—the shift of air flow too abrupt, his wrist angle short by a fraction, his breath misaligned by a heartbeat.
Mistakes that once took days to sense—now fixed in moments.
As the sun sank behind the mountains, Giyu finally felt it click.
He inhaled sharply, his chest expanding to its limit, and then released.
"Water Breathing… Eleventh Form!"
It was the first time he spoke that name in this life.
The Nichirin Sword cut through the air, forming a flawless circle around him.
A ring of azure water burst forth, spinning seamlessly from the tip of his blade, linking end to end in a perfect flow that enclosed him completely.
The Eleventh Form—Dead Calm.
The water ring spun rapidly, rumbling with a low hum as the air struck its surface and was instantly deflected.
He held the stance until his breath ran dry. Only then did the ring begin to fade, dissolving slowly into mist.
Tomioka Giyu sheathed his sword, his chest rising and falling heavily.
Even though the technique lasted only a moment, the physical strain it demanded far exceeded any other form.
"What was that?"
The voice came suddenly from behind him.
Giyu turned to see Urokodaki Sakonji standing under the eaves, the tengu mask facing straight toward him. The old man had clearly been watching for some time.
"It's… a new breathing form," Giyu said, uncertain. After all, this was his first time performing it in this lifetime.
In the history of the Demon Slayer Corps, creating a new form of an existing Breathing Style was almost unheard of—especially Water Breathing, one of the oldest and most refined techniques.
From the First to the Tenth Form, each had been honed over generations by countless Water Hashira, leaving almost no room for improvement.
Urokodaki walked forward in silence.
He didn't look at Giyu, but instead at the ground—the faint circular mark still glistening where the water had been.
"You just called it… the Eleventh Form?"
His voice was hoarse.
"Yes."
Giyu nodded.
"I wanted it to be a form of absolute defense—something that could block attacks from every direction."
Urokodaki snapped his head up. Even through the mask, Giyu could feel the weight of his master's shock.
"Absolute defense…"
He repeated the words slowly, as if testing their meaning. After a long pause, his tone grew stern.
"Do you have any idea what you're doing?"
"I do."
"Water Breathing has been passed down for centuries—from the Sengoku era until now. Every Water Hashira has worked to refine it," Urokodaki said, his voice heavy and sharp.
"From the First Form to the Tenth, each one is the result of generations of dedication and bloodshed. No one has ever tried to add another form—because there's never been a need to!"
His hands trembled slightly as he pointed toward the ring-shaped mark on the ground.
"Are you telling me… you created this yourself?"
"Yes."
Giyu met his gaze without flinching.
"In battle, I found that the current forms weren't enough for defense. Against opponents with overwhelming speed, it's hard to adjust the stance in time. So I thought—"
"So you created a new one?" Urokodaki interrupted, his tone rising with disbelief.
"Do you even understand what that means, Giyu? This isn't a child's game! Each breathing form requires precise theory, endless trial, and absolute control. Even the slightest mistake could destroy your own body!"
Giyu didn't argue.
He knew his teacher's fear wasn't unfounded.
The essence of Breathing Styles lay in manipulating the body through deliberate rhythm. A single breath mistimed could strain the organs, tear muscle fibers, or even rupture veins.
But Giyu was confident.
With the experience he carried from the future, his understanding of breathing far surpassed anyone in this era.
He knew exactly how the Eleventh Form worked—and how to align his breathing perfectly with it.
"I've practiced it many times," he said calmly.
"The rhythm and blade motion are synchronized. It won't harm me. And… it truly works as a defense."
Urokodaki stared at him for a long time—so long that Giyu half-expected to be scolded or struck for his arrogance.
But instead, the old man exhaled a deep sigh. The sound filtered through the mask, carrying exhaustion and quiet wonder.
"You really are…" He shook his head. "A child whose talent defies belief."
Turning away, he walked back toward the eaves, his back facing Giyu.
"Continue your training. But remember—don't use that Eleventh Form in front of others."
"Yes."
"And one more thing…" Urokodaki paused. "Give it a name."
Giyu blinked, then looked down at his sword. "Then… 'Dead Calm.'"
Dead Calm—the calm after the storm.
When this form was used, no matter how fierce the surrounding chaos, within it there would always be perfect stillness.
Urokodaki didn't turn back, only gave a quiet "Mm," his voice soft with approval.
As the sun sank completely, night settled over the training ground.
Giyu stood once more in the clearing, gripping his Nichirin Sword tightly.
More than half a month had already passed.
Sabito's memorial day was drawing near.
He lifted his eyes toward the upper falls.
There, hidden among the trees, lay a small graveyard—where everything he had once lost still rested.
In his past life, he had missed Sabito's memorial because of a mission. The regret had stayed with him for years.
This time, he wouldn't miss it.
Giyu took a long breath and assumed the Water Breathing stance again.
Under the pale moonlight, the sword flashed. The Eleventh Form—Dead Calm—bloomed silently around him, a ring of still water rising and fading into the night.
His training was far from over.