When Tomioka Giyu arrived at the Echigo outpost, snow was falling.
The outpost was a renovated old relay station, standing quietly on the edge of a small town at the mountain's base. A plain wooden sign hung above the entrance, marked with a small carved symbol of "mizu" (water).
As he slid the door open, warm air mixed with the faint scent of sake brushed against his face.
Three Demon Slayer swordsmen, all dressed in Corps uniforms, were seated around a sunken hearth. The moment they saw Giyu, they rose to their feet.
"Tomioka-sama!" they called out in unison, their tone respectful and nervous.
Giyu gave a short nod, removed his snow-dusted haori, and hung it on the hook by the door.
"Report your names and Breathing Styles."
The man on the left was tall and dark-skinned, his hands calloused like a farmer's.
"Tanaka Hei, sir. I use the basic forms of Stone Breathing."
The man in the middle was of medium build, sharp-eyed, and quick in movement.
"Sato Shin. I use the First through Third Forms of Wind Breathing."
The one on the right was a short, baby-faced boy, barely fifteen or sixteen.
"Suzuki Jiro. I can use the First and Second Forms of Thunder Breathing."
Giyu listened quietly, then walked to the hearth and sat down.
"You should all know the local conditions better than I do. Tell me what's been happening recently."
Sato stepped forward and produced a folded slip of paper from his uniform. "This is a list of missing persons over the past month. The disappearances are concentrated in several northern villages—always on snowy nights.
No traces left at the scenes, but claw marks were found beneath the eaves."
Giyu unfolded the paper. The handwriting was messy, but the information was clear.
"How large were the claw marks?"
"Broader than a man's hand," Tanaka said grimly. "And the tips had backward hooks."
"We think it's a demon adapted to the cold," he added. "It climbs easily and probably hides deep in the mountains."
Suzuki hunched his shoulders and spoke softly. "We tried searching last month. Got lost in a blizzard—barely made it back. It felt like that demon could control the snowstorm itself."
Giyu refolded the report and tucked it into his chest pocket.
"Starting today, you'll train every morning—basic Breathing exercises. I'll be watching."
The three looked stunned. They clearly hadn't expected the newly assigned Water Hashira to focus on training before missions.
But none dared question him. "Yes, sir!" they answered in unison.
For the next month, the courtyard echoed each morning with the steady rhythm of breathing.
Giyu stood beneath the veranda, his eyes sharp as he observed them.
Tanaka's Stone Breathing was rigid and heavy—solid but without flexibility.
Sato's Wind Breathing was impatient—his flow shallow, explosive but unsustained.
Suzuki's Thunder Breathing lacked rhythm—his First Form was too slow, his Second Form too unstable.
"Tanaka, loosen your shoulders when you inhale. Stone isn't lifeless—it's the mountain's strength with give and flow."
"Sato, exhale slower. Let the wind coil around your blade, not scatter into the air."
"Suzuki, Thunder's essence is rhythm, not speed. Keep the breathing intervals steady first."
Giyu's instruction was sharp and precise, cutting straight to the core of their weaknesses.
He didn't teach them new forms—only corrected their breathing and application.
With his knowledge from the future, he could easily identify the flaws in each swordsman's technique and guide them to fix it in the simplest way possible.
After one month, the progress was visible.
Tanaka's strikes had grown firm yet elastic, carrying a hidden weight.
Sato's draw speed nearly doubled.
Suzuki's Thunder Breathing finally had the snap of real lightning.
"Tomioka-sama, your teaching's unbelievable!" Suzuki said, rubbing the back of his neck with a grin.
Giyu didn't respond. He only said, "Starting today, the three of you will work as a team. Search the outskirts of the northern villages, but don't enter the mountains. Return before sunset."
"Yes, sir!"
Once they departed, Giyu strapped his Nichirin Sword to his back and headed alone toward the snow mountains.
The cold in Echigo was sharper than he'd imagined.
The wind bit at his face like a blade, his breath turning instantly to mist.
The snow reached his knees—each step heavy, each movement slow.
He wasn't training forms now—he was training to maintain Breathing under extreme cold.
The Upper Moon Two, Douma, made his home in the northern lands—where snow and ice never melted.
In his previous life, Kocho Kanae had fought and died in that same frozen domain.
Giyu didn't know if he could change the outcome this time. But he had to be ready—
Even if his lungs froze, even if his limbs went numb, Water Breathing could not falter.
He took a deep breath and began to run through the snow.
The icy air stabbed into his lungs like shards of glass.
His breathing rhythm broke immediately, the flow of Water Breathing faltering.
He forced himself to slow down, focusing on control—each inhale drawn deep, each exhale released steady and long.
Once. Twice. Three times.
Pain filled his chest, his throat felt scorched dry.
But he didn't stop. His pace even quickened.
The snow crunched beneath his feet, leaving a deep trail behind him.
He began to practice with his blade mid-run.
"Water Breathing, First Form: Water Surface Slash!"
The blade flashed. Snow sprayed aside in a clean cut—but its power was down by a third.
Not enough.
He pressed harder, quickening his breathing.
The pain in his lungs became searing, his vision darkened at the edges.
Yet the path of his breathing grew clearer in his mind—
How air entered his nose, flowed down the trachea, filled the lungs, cycled through each lobe, and finally released power through his blade.
After three days, he could run through snow for half an hour without losing rhythm.
After five days, he could perform the first five Forms of Water Breathing in freezing air.
After seven days, he attempted the Eleventh Form—Dead Calm—within a blizzard.
A faint blue water ring formed within the storm. Though smaller than usual, it held steady, blocking every flake of snow that struck it.
Standing amidst the swirling wind and frost, Giyu's chest rose and fell sharply, yet a faint curve tugged at the corner of his lips.
He was improving faster than expected—but it still wasn't enough.
Douma's strength far surpassed that of an ordinary Upper Moon. Giyu needed stronger control—absolute mastery.
He turned, ready to head back toward the outpost, when his gaze froze.
Down the slope of the mountain ridge, something red stood out.
It wasn't the white of snow or the black of trees—it was a vivid, warm shade of red that burned quietly against the cold landscape.
Giyu frowned slightly and instinctively began walking toward it.
The wind and snow lessened, the drifts underfoot thinning with each step.
He passed through a grove of pines, and the view ahead opened up—
At the base of the mountain stretched a small, open clearing. Several wooden houses stood neatly spaced apart, roofs blanketed in thick snow, thin trails of smoke rising from their chimneys.
The red color came from a strip of fabric hanging outside one of the houses—a striking shade of crimson, waving faintly in the cold breeze.
This place… looked familiar.
Giyu slowed his pace. His eyes swept across a small vegetable patch, a pile of chopped firewood, and strings of peppers and corn hanging from the eaves.
No mistake.
This was… Kamado Tanjiro's home.
He stopped dead in his tracks.
If his memory served him right, Tanjiro was still just a normal boy at this time—spending his days cutting firewood with his father, carrying charcoal down the mountain to sell in the village.
There were still three years left until that night.
Too early.
Meeting Tanjiro now meant nothing.
Worse—it might disrupt everything.
He couldn't risk it. Not yet.
Giyu turned to leave, intending to disappear without a sound.
"Excuse me, sir—please wait a moment."
The voice that came from behind him was warm and calm, carrying the unpolished tone of someone who lived their life in the mountains.
Giyu froze.
He slowly turned around and saw a man standing in the doorway of the wooden house, a bundle of firewood on his back and a thin layer of snow resting on his shoulders.
The man had the same crimson hair as Tanjiro—only shorter—and a faint scar crossed his forehead, as if from a long-healed wound.
His expression was gentle, his eyes filled with kindness, free of suspicion.
"It's freezing out here," the man said, brushing snow from his sleeve. "Did you come down from the mountain? You look like you've been out a while. Why not come inside for a bowl of hot soup to warm yourself?"
Giyu stared at him, momentarily unable to speak.
He knew this man.
Kamado Tanjuro—the father of Kamado Tanjiro. A frail man, yet one known for his unmatched endurance—able to remain motionless in the snow for days without food or water. A man who, according to stories, had once danced with the sun itself.
In his previous life, Giyu had only heard Tanjiro's words about his father. He had never imagined meeting him here—in this time.
"No need," Giyu said at last, his voice stiff and low. "I was just passing through."
Tanjuro smiled, unbothered by his cold tone.
"Passing through or not, it's too cold to stay outside. Come in and rest a bit. My wife just finished making miso soup—it's still hot."
He stepped aside, opening the doorway wider. His gaze flicked to the Nichirin Sword at Giyu's waist, a quiet glimmer of understanding passing through his eyes, though he asked nothing about it.
Giyu looked at the man's kind smile, then at the warm light spilling from inside the home. For the first time, he hesitated.
He should leave. He knew that. The timeline must remain undisturbed.
But… that bowl of soup—it might really help drive the cold from his body.
And a part of him couldn't help but wonder—what kind of man had raised a child like Kamado Tanjiro?
The wind picked up again, scattering ice and snow against his face, stinging sharply.
After a few seconds of silence, Giyu finally gave a small nod.
"…Thank you."
Tanjuro's smile brightened. "No trouble at all. Please, come in."
Giyu followed him inside. Warm air rushed to meet him, carrying the rich, comforting scent of home-cooked food. The cold in his limbs began to fade instantly.
The house was modest but spotless. A fire burned steadily in the hearth.
A woman wearing an apron stood by the pot, ladling steaming soup into bowls. When she saw them come in, she lifted her head and smiled gently.
"Husband, who is this?"
"A traveler from the mountains," Tanjuro said. "He got lost. I invited him in to warm up."
He guided Giyu to a cushion by the hearth. "Please sit. I'll call the children to come meet our guest."
Giyu sat quietly, the flickering warmth of the flames reflecting in his eyes. Watching the simple peace of the scene before him stirred something deep within his chest.
He knew this warmth was fleeting.
But for now—at least now—it was real.
A bowl of steaming miso soup was placed gently in his hands. The woman's voice was soft. "Please, drink while it's hot. It'll warm you right up."
Giyu accepted it, the heat seeping into his fingers.
He looked down at the swirling steam rising from the bowl—and for the first time in a long while, he thought that maybe… staying for a little while wouldn't hurt.