Behind the Butterfly Mansion, the morning mist had yet to lift from the training field. Wooden posts and practice demon models stood scattered across the open ground, the air thick with the mixed scent of sweat and wisteria.
Tō stood in the center, gripping his Nichirin Sword with one hand. The sleeve of his black uniform hung empty—his left arm wrapped tightly in layers of bandages, secured up to the shoulder, leaving only his right arm free.
"Again!"
Uzui Tengen's sharp voice rang out from the side. His silver headband fluttered in the morning breeze as his keen gaze followed Tō's every movement.
"During the third strike from that dummy demon, you dodged half a beat too slow—
if that had been a real demon, your stomach would already be split open!"
Tō exhaled heavily, wiping the sweat from his forehead before tightening his grip on his sword once more.
Ever since losing his left arm, he could no longer wield the blade with both hands.
Most of his Storm Breathing techniques had become useless—
moves like Reversing Whirlpool Slash and Wave-Cutting Wind Break required the strength of both arms. Now, he couldn't even perform the opening stance.
Still, to bring back Giyu and fight alongside Tanjiro and the others,
he had sought out the Sound Hashira, pleading to learn the Musical score technique—
a skill that enhanced evasive rhythm and movement.
"Remember, the musical score isn't just memorizing attack motions—it's reading the rhythm,"
Tengen said, stepping beside the dummy demon and tapping its wooden joint.
"Look here—its right arm always pauses 0.3 seconds before each swing. That's an note.
Its footwork moves in two-step bursts, attacking every second step. That's the beat.
What you need to do is connect those notes and beats into a mental score—
predict the rhythm, and move one step ahead into the safe zone."
Tō nodded, closing his eyes as he recalled the dummy's previous sequence—
first a horizontal slash (pause 0.3 seconds),
second a vertical strike (after a two-step advance),
third a diagonal cut (pause 0.2 seconds, faster than before).
In his mind, he drew a flowing line, each node marking a strike point,
the gaps between them—the routes for his evasion.
"Start!"
At Tengen's command, the mechanism inside the dummy clicked to life.
Its right arm whipped up, slicing the air in a wide arc.
Tō focused on its joint. In that brief pause before movement, he slid sideways like drifting willow fluff—
barely escaping the sweeping strike.
The dummy advanced two steps, then brought down its left arm in a vertical slash.
Tō had already anticipated this—he tapped the ground with the tip of his foot and leapt backward.
The blade in his hand rotated lightly, the flat of the sword catching the dummy's wooden weapon.
"Good! You've got the rhythm right this time!"
Tengen's eyes gleamed with approval. "But it's not enough! You're just following the rhythm—
you need to lead it! After dodging, find the gap to strike back!"
Before the words faded, the dummy's pace suddenly quickened.
Its arms alternated strikes, shifting from a two-step to a three-step rhythm.
Its pauses shortened to 0.1 seconds.
Tō's breathing hitched. The mental score in his head began to break apart.
He was half a beat too late—the dummy's wooden blade grazed his ribs, leaving a shallow red mark.
"Hh—"
He hissed through his teeth but didn't stop. Instead, he tightened his grip and reset his stance.
"Again!"
He remembered lying in bed at the Butterfly Mansion three months ago,
staring at the empty space where his arm used to be—his first real taste of despair.
It was Tanjiro who held his hand, saying, "Tō, we'll get stronger together."
It was Shinobu who handed him the medicine, saying,
"Your Storm Breathing is special. Even with one arm, you'll find your own way."
"Haah!"
With a low shout, Tō charged again.
This time, he didn't try to memorize each pause. Instead, he let his breathing synchronize with the rhythm of the dummy's strikes.
Storm Breathing, attuned to the wind, excelled at sensing changes in air flow.
He used the gusts created by the dummy's movements to read its direction.
In his mind, the score turned from rigid lines into flowing waves.
Each movement became smoother, more instinctive.
When the dummy slashed horizontally, he slid with the wind.
When it struck downward, he used the lift of the air to leap.
When it swung diagonally, he spun along the current—
and during each motion, his sword brushed the dummy's joints, disrupting its rhythm.
"That's it!"
Tengen clapped once, signaling the mechanism to stop.
"You've got it now! The essence of the musical score is resonance—
resonate with the enemy's rhythm, with your own breathing. That's how you find your chance to counterattack."
He gestured at the dummy. "Now, try using one arm. Combine the rhythm you've learned—
attack its joint directly."
Tō inhaled deeply. Storm Breathing swirled through his body,
his right arm drawing all his strength into focus.
Locking onto the dummy's right shoulder joint, he dashed forward just as it raised its arm.
His blade flashed with faint wind trails. "Storm Breathing: Modified—Instant Thrust!"
It was a move he had reworked for one-handed use—
sacrificing raw power for speed and precision, relying on rhythm prediction to strike at the perfect instant.
The wooden blade pierced the dummy's joint cleanly.
A soft click sounded, and its right arm froze mid-motion, unable to move again.
"I did it!"
A rare smile spread across Tō's face. Sweat streamed down his cheek,
but strength surged through his body like wind.
Tengen stepped forward, patting his shoulder—careful to avoid the bandaged side.
"Not bad, kid. You're tougher than I thought.
Anyone else losing an arm would've given up—but you carved out your own path instead."
He paused, then pulled a folded sheet of paper from his pocket and handed it to Tō.
"This is my Musical Score notebook. It's got the attack rhythms of different demons recorded in it.
Study it well. Next training, I expect you to handle two dummy demons at once."
"Thank you, Uzui-san!"
Tō took the paper carefully, gripping it with his right arm while keeping the gesture of using both hands—a habit he hadn't let go of. His eyes burned slightly.
Just then, a Kakushi sprinted toward them, holding a sealed letter.
"Tō-san! A message from Tanjiro-san! He says there are demon sightings in the northern region—villagers missing. He's requesting your help!
He mentioned you've patrolled the north before with the Water Hashira and know the terrain well!"
Tō's chest tightened. The northern region—
——That was the patrol zone Giyu once managed, now overseen by Tanjiro after taking the position of Nichirin Pillar.
Tō tore open the letter immediately. Tanjiro's handwriting was firm and precise:
"Tō, in Aoyagi Village of the northern region, five villagers have gone missing in the past week.
Traces of faint blue demon energy were found at the scene—it may be linked to an Upper Moon.
I've already departed with Zenitsu and Inosuke. If your training is complete, come to Aoyagi Village as soon as possible to meet us."
"Uzui-san, I—"
Tō looked toward Tengen, eyes filled with urgency.
"Go," Tengen said, waving a hand with a confident grin. "It's the perfect chance to test your musical score in the field.
And remember—the heart of rhythm isn't rigidity, it's life.
If it gets dangerous, don't force it. Dodge when you can. Retreat if you must. Only the living can protect others."
"Yes, sir!"
Tō nodded hard, tucking both the notebook and letter against his chest. Grabbing his Nichirin Sword, he sprinted toward the village gate.
As he ran, the paths of the northern region replayed in his mind—
Aoyagi Village lay deep in a valley, marked by an old locust tree at its entrance and a sheer cliff behind it.
He and Giyu once rested under that tree during patrols, and it was there Giyu had taught him how to recognize herbs that grew along the cliffside.
Did Giyu still remember those days?
By sunset, Tō finally reached Aoyagi Village.
Under the old locust tree, Tanjiro, Zenitsu, and Inosuke were questioning a villager.
Spotting Tō, Tanjiro immediately brightened and hurried over.
"Tō, you're here! How's your training going?"
"Good. Uzui-san taught me the musical score—I can predict attacks now."
Tō smiled briefly, turning toward the villager.
"Sir, where did the missing people disappear?"
The man, pale and trembling, swallowed before speaking.
"All near the cliff behind the village… At night, you can hear strange winds from that direction. By morning, someone's gone.
All we ever find are faint blue traces—nothing else."
"Faint blue demon energy…"
Tanjiro frowned, locking eyes with Tō. Both knew what that color could mean.
Giyu's Blood Demon Art emitted the same blue whirlpools of energy.
"But Giyu-san is Mushiki now—he shouldn't be attacking villagers. It might be another demon."
Zenitsu folded his arms, his expression tense.
"Could it be an Upper Moon? Blue aura… Gyokko was blue, and so is Giyu-san…"
"Doesn't matter what it is—we'll check it ourselves."
Inosuke unsheathed his blades, excitement flaring in his eyes.
"I'll test out my new technique!"
The four followed the villager's directions toward the cliff behind the village.
The path narrowed the farther they went. Tall grass brushed their legs on either side, and faint specks of blood stained the dirt.
Tō led the way, sword in hand, senses sharp. In his mind, he began forming an environmental score—
the sway of the grass (the rhythm of the wind),
the position of stones (the anchor points for evasion),
the updrafts from the cliffside (possible directions of attack).
"Stop."
Tō froze suddenly, lowering his voice.
"There's something ahead. The aura's faint—but dangerous."
Tanjiro nodded, signaling everyone to crouch.
They crept forward through the tall grass until the cliff's edge came into view—
beside a boulder stood a tall, thin figure wreathed in faint blue demon energy, a long blade in his hand.
He was hunched over, gnawing on something.
"A Lower Moon," Tanjiro whispered, his mark glowing faintly.
"His aura's stronger than a normal demon—he must've just been promoted!"
Before they could move, the figure's head snapped up, crimson eyes gleaming.
"Well, look at that… little slayers coming straight to me. Perfect timing—my Blood Demon Art isn't fully trained yet. You'll make good practice!"
He swung his blade sharply. Faint blue air blades whipped through the air.
"Blood Demon Art: Wind Cutter!"
"Sun Breathing, Fifth Form—Setting Sun Transformation!"
Tanjiro's sword flared with heat as he met the attack head-on. Flame and wind clashed, sparks scattering wildly.
Zenitsu burst from the side, lightning sparking through his blade.
"Thunder Breathing, First Form—Thunderclap and Flash: Godlike Speed!"
A streak of gold cut toward the demon's back, but the demon twisted away, sliding left to avoid the strike.
He countered instantly, swinging another air blade at Inosuke.
"Beast Breathing, Third Fang—Devour!"
Inosuke roared, his dual blades crashing into the gust with a burst of shattered stone.
Tō still hadn't moved. His eyes stayed fixed on the demon's motions.
The rhythm revealed itself—four-step pattern.
Each strike followed a subtle shoulder drop—a 0.2-second delay before swinging.
The air blades curved forward, covering a three-meter arc.
The score formed quickly in his mind. The weakness was clear.
After each Wind Cutter, there was a 0.5-second pause for recovery—a perfect counter window.
"Tanjiro! Make him use his Blood Demon Art again!"
Tō's shout carried through the roar of wind as he steadied his breathing. Storm Breathing surged through his right arm.
Tanjiro immediately understood. His Nichirin Sword blazed with orange fire.
"Sun Breathing, Seventh Form—Beneficent Radiance!"
The demon took the bait, swinging again.
Another Wind Cutter cleaved through the air, colliding with Tanjiro's flames in a burst of heat and wind.
And in that fleeting instant—when the gusts scattered and the demon inhaled to recover—Tō moved.
He sprang forward, using the cliff's updraft to propel himself.
His one arm swung the blade in a fluid arc, the air itself curling around the strike.
"Storm Breathing: Modified—Wind-Breaking Slash!"
The blade cut true.
The demon's eyes widened, panic flashing across his face.
"How… did you—predict—"
Before he could finish, his head hit the ground. His body crumbled into ash.
Tō stood by the cliff, chest heaving, his right arm trembling slightly.
It was the first time since losing his left arm that he had performed a beheading alone.
The technique was simple—but it felt more satisfying than any victory before.
"Tō! That was amazing!"
Zenitsu ran up, eyes wide with admiration.
"That slash was so fast—I couldn't even see it!"
Inosuke clapped him hard on the shoulder.
"Not bad! Even with one arm, you're still this strong! Next time, we're sparring!"
Tanjiro smiled, pride shining in his eyes.
"Tō, your musical score worked! From now on, we'll only keep getting stronger—together."
Tō nodded, then turned toward the cliff.
Far below, in the depths of the valley, a faint blue shadow flickered—
a trace so subtle yet so familiar that it sent a chill down his spine.
Was that Giyu?
Had he been watching all along?
"What's wrong, Tō?" Tanjiro asked softly.
"Nothing," Tō replied, shaking his head with a faint smile.
"I just feel… we're getting closer to Giyu-san."