In the forest behind Mount Momoyama, as winter receded and warm spring took hold, branches sprouted buds and flowers. A recent stretch of rain had awakened all things with renewed vitality.
Pink peach blossoms blanketed the mountains.
Boom—!
A thunderous crash suddenly echoed through the mountain path, startling sparrows from the treetops and sending petals fluttering down.
It was the sound of a massive wooden pendulum slamming into an ancient tree. Its immense weight granted it terrifying speed—one swing could easily send an adult flying, or even kill if struck directly.
Yet such fearsome impacts continued in steady succession.
Boom, boom, boom—
The rhythm formed a beat across the mountains.
Or perhaps it truly was a rhythm.
For someone was dancing within it—her movements like a spirit of the forest.
Clad in a vermilion haori, the girl moved gracefully. Her slender body always slipped away at the very instant before the wooden pendulum could strike. Her black hair flowed like spilled ink.
After arriving at Mount Momoyama, she had cut her former ornate kimono into this haori. Golden crane patterns fluttered like wings taking flight.
Here, it seemed nothing could harm her.
"Mm."
From the mountaintop, the old man watching gave a satisfied nod.
The girl who once knew nothing had, in just two months, grown into a swordsman worthy of his praise.
From the chill of early spring to the warming days now, every morning before sunrise he would wake Sui, bring her into the trap-filled forest, and train her. In the afternoons and evenings, he taught her swordsmanship.
The essence of Thunder Breathing was speed—striking like lightning, severing an enemy's head in the blink of an eye.
And Sui had learned well.
So well that after only two months, Kuwajima felt there was little left for him to teach.
Crack—!
A sudden peal of thunder shook the peach grove. Faint arcs of dark violet lightning flickered in the air.
Sui appeared beside the old man and sheathed her blade.
At the same time, every falling petal in the grove split cleanly in two.
"You've improved again."
Kuwajima smiled.
"That's thanks to your teaching."
Sui replied naturally.
Only up close did one notice—
Her eyes were closed.
Long lashes rested like butterfly wings, softening the eerie beauty of her features with a quiet serenity.
This had been Kuwajima's idea.
At the beginning of her training, all his carefully arranged mechanisms had been destroyed. With just a flick of her finger, she could split massive wooden pendulums cleanly in half, their cuts smooth as mirrors. Ground traps fared even worse—her Mystic Eyes saw through and dismantled them effortlessly.
Whenever danger arose, her instinct wasn't to evade—
It was to open those eyes and erase everything.
Even without a blade.
This had astonished the old man.
Those eyes were beyond reason. Without a weapon, the girl herself became one—everything around her, even her own body, turning into the reaper's scythe.
So after repairing the mechanisms, Kuwajima simply made her train with her eyes closed. In the early days, he stayed by her side, and whenever she opened her eyes—Mystic Eyes or not—he would strike her head with his cane.
Thankfully, he hadn't knocked her senseless.
"Thunder Breathing is bold and unrestrained. It belongs to those swift as lightning. Among all Breathing styles, it is the fastest, with the greatest explosive power—but it also demands the highest physical ability, making it extremely difficult to master."
The old man spoke slowly, then glanced at her.
After two months of training, her figure had grown more refined, taller and more slender than when she first arrived. He now had to tilt his head slightly to "look" at her.
Sui remained calm as ever.
"You've said that before."
"Just reminiscing. Among all my students, your talent is the most frightening. Even without those eyes, you would still be worthy of inheriting Thunder Breathing."
He turned his back.
"Come to think of it—how long has it been since you last opened your eyes?"
"About a month."
Sui considered.
Once she overcame her instincts, sight itself became almost unnecessary.
Though it began as a training method, she found it unexpectedly fitting. Lightning appeared before thunder arrived—understanding the world didn't always require seeing it.
The clearer her perception of everything became, the more "lines" of death her Mystic Eyes would reveal.
Breathing techniques greatly enhanced her senses. Even with her eyes closed, she could grasp reality with clarity.
Sometimes, eyes could deceive.
Perception would not.
For example—
Right now, she could feel the rising intent to fight within the old man.
"You want to spar with me?"
Sui asked.
A flicker of surprise crossed Kuwajima's face, quickly replaced by a grin. His beard bristled as the aura of a Hashira surged around him.
He gave no verbal answer.
Because the cane sweeping toward her spoke louder than words.
Sui raised her sheathed sword to block, using the force to retreat.
Kuwajima was a former Thunder Hashira. She was fast—but he would only be faster. There was no reason to doubt Hashira's strength, so she immediately created distance.
The old man withdrew his cane and assumed an iaido stance.
It was hard to imagine a wooden cane forming a sword stance—but looking at him now, the only word that came to mind was:
A blade.
A blade yet to be drawn.
His body lowered slightly, muscles tightening. The immense power hidden within his small frame surged forth like a flood breaking through a dam.
"—Haaah—"
Sui focused.
She heard it—
A long, rolling breath like distant thunder.
No wonder he had said Thunder Breathing required a bold spirit.
Kuwajima embodied it.
Even in old age, even unable to fight on the battlefield, that fierce passion still burned within him. He had spent too long in peace—and too long restrained.
Students were still just students.
None could truly spar with him.
But today—
After witnessing Sui slice through the falling blossoms—
He placed her on equal footing.
This old blade had lain dormant for too long.
At last, it had found an opponent worth testing against.
"Still not opening your eyes?!"
he roared, his voice rumbling like thunder itself.
Opposite him, Sui stood quietly.
Eyes closed.
Calm as if asleep.
"No."
She answered.
She drew her blade.
Golden lightning coursed along its surface—the sword he had lent her, once his own weapon used to slay countless demons.
Kuwajima moved.
Thunder roared.
A streak of golden lightning shot forward, splitting heaven and earth like a blade.
So fast.
He vanished from Sui's perception.
She raised her sword. It traced a crescent arc through the air as dark violet lightning burst forth.
In an instant—
A metallic clash exploded in her ears.
The collision between Nichirin blade and wooden cane rang like steel striking steel.
"Thunder Breathing, Fourth Form: Distant Thunder."
A faint stream of air flowed from Sui's breath.
Her vermilion haori was instantly wrapped in dark violet lightning. The arcs coiled like serpents, then erupted—
She knocked aside the old man's cane.
Lightning descended from above with heaven-splitting force—
A horizontal slash.