In the morning light, the metal banner of the Sound Hashira Training Area fluttered sharply in the wind.
Uzui Tengen stood at the center, arms crossed, with a pile of twenty-jin iron weights stacked at his feet.
In front of him stretched a long track, scattered with waist-high wooden hurdles and shallow pits filled with water. The air buzzed with tension—
this was his own creation: the Rhythm Endurance Trial.
Each trainee had to run three full laps while carrying weights, dodging every obstacle along the way, and—most importantly—maintaining perfect breathing rhythm.
If the rhythm broke even once, they'd start over.
"First group: Zenitsu, Inosuke, and you three—step forward!"
Tengen's booming voice echoed through the field, his silver headband gleaming as it swayed.
Zenitsu groaned under his breath, "Here we go again…," but he didn't delay.
After months of special training with Tanjiro, weighted runs had become part of his routine.
The twenty-jin load wasn't easy, but it wasn't unbearable either.
Inosuke, on the other hand, slung the heavy iron across his shoulders with excitement, Beast Breathing pulsing through his body.
Muscles flexed tightly beneath his uniform. "This isn't even heavy! The great Inosuke-sama could run five laps easy!"
At the signal, all five charged forward.
"Headlong rush!"
Zenitsu lagged slightly behind at first, but as soon as he steadied his rhythm with Thunder Breathing, his pace evened out.
He recalled Tanjiro's words—"Stable breath, stable steps."
Sure enough, his every inhale and exhale synchronized perfectly with his footfalls, and before long, he caught up to Inosuke.
Inosuke, pure instinct and muscle, leapt over each hurdle like a wild beast and skimmed across the edge of water pits without losing rhythm.
The two ran side by side, maintaining their breathing forms across all three laps, leaving the rest of the group far behind.
One trainee even knocked over a hurdle and had to resign himself to an extra round of punishment laps.
"Not bad! You've got solid basics!"
Tengen tossed each of them a palm-sized metal device.
"These are Rhythm Sensors. Clip them to your wrists.
Next up—dodge the wooden arrows while keeping your breathing perfectly synced to the vibration rhythm.
My training principle is simple—maintain rhythm in the middle of chaos!"
Without warning, wooden arrows shot from both sides of the field, fast and from unpredictable angles.
Zenitsu steadied his breath. The golden current of Thunder Breathing pulsed in sync with the sensor's vibration, and his body moved like lightning.
Each sidestep, twist, and leap landed with pinpoint precision, dodging the flurry of arrows.
Inosuke relied on his primal instincts, combining the wild sensitivity of Beast Breathing with the rhythmic pulse of the device.
His movements were rough but accurate—every arrow missed.
"Qualified! Head over to the Flower Hashira next!"
Tengen waved them off, the corners of his mouth lifting in rare approval.
When Zenitsu and Inosuke arrived at the Flower Hashira Training Area, Kocho Kanae stood on a wooden platform before a group of attentive trainees.
The soft pink hue of her uniform gave her a gentle air, though her eyes gleamed with focus as she held up a human-shaped model.
"In battle, continuous bleeding is dangerous," she said calmly.
"Today, I'll teach Breathing-Control Hemostasis—
by regulating your breathing rhythm, you can form a thin 'barrier' of air around a wound, slowing blood flow and compressing the vessel."
As she spoke, Kanae took a dull-edged knife and drew a shallow cut across her forearm. Blood instantly welled up.
Then she inhaled deeply for three seconds, held for one, exhaled for five, and gathered the faint pink aura of Flower Breathing around the wound.
In less than ten seconds, the bleeding stopped completely.
"Amazing!"
The trainees couldn't help but gasp. Zenitsu even forgot to complain, pushing forward to get a closer look.
Kanae smiled and had everyone pair up, making small, shallow cuts on their arms (barely breaking the skin) to practice the technique.
Inosuke went first—but his breathing was too erratic, and the blood kept flowing.
"Don't rush, Inosuke," Kanae said gently, resting a hand on his shoulder.
"It's not about strength—it's about control.
Imagine your breath as a fine net, wrapping softly around the wound. Follow my rhythm…"
Following her instructions, Inosuke steadied his breathing, and this time, the flow stopped quickly.
He raised his arm high, grinning wide. "The great Inosuke-sama did it! Wahahaha! I'm unstoppable!"
Zenitsu learned even faster—Thunder Breathing was built on precise control of air.
He inhaled, focused his golden energy over the wound, and within five seconds, the blood flow halted.
"Excellent work, Zenitsu!" Kanae praised, then continued in a firmer tone.
"Now, we'll move to Breathing-Control Adrenal Surge.
By releasing a burst of intense breath in a short span,
you can trigger a surge of adrenaline—temporarily increasing your speed or strength by roughly thirty percent.
It's a last-resort survival technique. Use it sparingly—
once it wears off, your body will be left weak and drained."
As she demonstrated, a soft pink aura flared around her, and her speed instantly doubled.
The trainees followed along. When Zenitsu activated Thunder Breathing, golden lightning flickered around him, and his movements became so fast that afterimages lingered in the air. When Inosuke used Beast Breathing, his muscles swelled slightly, and his fist struck the wooden post so hard it left a shallow dent.
"Good, everyone's got it!"
Kanae nodded approvingly.
"These two techniques are meant to help you survive. As long as you live, you can keep fighting. Now, head to the Sun Hashira—Tanjiro's probably getting impatient."
When Zenitsu and Inosuke pushed open the doors to the Sun Hashira Training Area, both froze for a moment.
The dojo was elegantly simple, its wooden floor polished smooth and low tables arranged neatly around the edges.
At the center sat Tanjiro, with stacks of rice crackers wrapped in oiled paper and a steaming teapot before him. When he saw them, he stood up with his usual warm smile.
"You're here! Come sit, have some hot tea and snacks first. Training will start soon."
The trainees hadn't expected Tanjiro's session to start like this. They gathered around eagerly.
Zenitsu bit into a cracker, the crunch echoing through the room. "Tanjiro, if training always came with rice crackers, I swear I'd never slack off again!"
"As if that'd ever happen," Tanjiro said with a laugh, handing him a cup of tea.
"Eat up and rest a bit. Today's training will need total concentration—it's heavy on the mind."
Inosuke gulped down his tea in one breath, then stuffed three handfuls of crackers into his mouth. "Tanbajirou! What're we waiting for? Start already! The great Inosuke-sama's ready to go!"
Once everyone had finished, Tanjiro stood at the center of the dojo and lifted a stack of black cloth bands.
"Today's training is about instinct.
In battle, an enemy's attack often moves faster than your thoughts. In that moment, it's not logic that saves you—it's your body's natural reaction to danger, your instinct."
He passed out the cloth bands. "Cover your eyes. I'll attack with a blunt wooden sword. Don't counterattack—just block or dodge.
And don't rely on sound. Feel it.
Sense the movement of air, the shift in breath. When danger comes, your body will always know before your mind does."
The trainees blindfolded themselves. Tanjiro tied his own cloth as well and picked up a wooden sword.
The orange-red aura of Sun Breathing glimmered softly around him. His control was flawless now—he could strike precisely without ever causing harm.
"Let's begin."
At his word, Tanjiro moved.
He approached a young trainee and swung lightly toward the trainee's shoulder. The boy tensed, unable to react in time, and the wooden blade tapped him.
"Relax," Tanjiro said gently.
"Don't think about where to dodge. Let your body move on its own. Try again."
This time, the trainee shifted left instinctively and avoided the hit.
When it was Zenitsu's turn, Tanjiro swung from behind. Zenitsu's nerves sparked instantly—his whole body jolted, and he leapt forward just in time to dodge.
"Perfect! That's it!" Tanjiro praised, grinning as he struck again and again. Zenitsu dodged every blow on instinct alone.
Inosuke, on the other hand, was even more extreme.
With his wild Beast Breathing unleashed and his sight taken away, his senses sharpened to their limits. The moment Tanjiro moved, Inosuke felt the air shift and dodged before the attack even came—sometimes even blocking from the opposite side mid-motion.
"Inosuke, you're insane!" one trainee gasped.
Inosuke lifted his chin proudly. "Of course! The great Inosuke-sama grew up in the mountains! This is child's play!"
The training continued for an entire hour.
At first, the trainees were hit again and again. But gradually, they learned to trust their senses—by the end, most could avoid nearly eighty percent of Tanjiro's strikes.
Tanjiro untied his blindfold, wiping sweat from his brow. "Instinct isn't something you're born with—it's something you build.
Keep sparring, keep training in real danger, and your body will start remembering what danger feels like."
He looked at Zenitsu and Inosuke with pride. "You two grew the fastest. Zenitsu, your instinct from Thunder Breathing, and Inosuke, your wild intuition—both are incredible strengths.
Keep pushing forward. We'll all get stronger together—so we can protect who we want to protect."
Zenitsu rubbed the back of his head, a little shy. "I didn't do anything special. I just moved when it felt dangerous, that's all."
Inosuke clenched his fists. "Tanbajirou! When training's done, we're sparring! I'll block every one of your strikes this time!"
Tanjiro laughed. "Anytime."
The dojo filled with easy laughter. The trainees gathered around Tanjiro, chatting excitedly about technique.
Sunlight poured in through the wooden windows, casting warm light across every smiling face.
Zenitsu looked around at his friends and thought that even if training was exhausting, as long as they all grew stronger together—it wasn't hard at all.
Meanwhile, deep in the Infinity Castle, Tomioka Giyu practiced alone in a silent hall.
His blade carved pale blue arcs through the air, the patterns of the moon flickering faintly along the edge.
For a moment, the image of Tanjiro and Tō flashed across his mind. His grip tightened.
The emptiness in his chest… felt just a little less hollow.