"Breathing Techniques?"
Nezuko blinked, momentarily stunned by Chika's suggestion. Then her eyes lit up, sparkling like twin gems. What girl hadn't once dreamed of becoming strong—or even a little cool? Even Nezuko, the sweetest of the sweet, felt that spark when she'd watched her siblings spar that morning.
But then her gaze wavered, her voice softening. "B-but… can I really learn it? Can someone like me do that?"
"Of course you can," Chika replied warmly. "If we could learn it, you definitely can. Right, Tanjiro?"
Tanjiro straightened immediately, as if handed a microphone. "Absolutely! Nezuko can do anything!"
He meant it, too. The thought of giving his sister even a sliver more power to protect herself—that alone was reason enough.
Nezuko's eyes rounded into adorable little dots. She spun in place with excitement, her bamboo muzzle bouncing slightly with the motion.
Meanwhile, Urokodaki was still sitting cross-legged in the living room, waiting for the three siblings to come eat.
"…They're taking forever," he muttered under his breath, exasperation radiating even through his Tengu mask. His entire aura seemed to grumble, "The food's getting cold, you know!"
Ten minutes later, the trio finally shuffled in, heads lowered like scolded children.
Chika, especially, felt an odd pang of guilt—mostly because she distinctly remembered saying the exact same words to her younger siblings back home.
After sitting down, they wasted no time sharing their latest idea with Urokodaki: letting Nezuko learn Breathing Techniques.
The old man froze mid-sip. His mask tilted up slightly, revealing half his face—just enough for them to see his expression twitch. He very nearly spat out his miso soup.
A demon… learning Breathing?
That thought had never once crossed his mind. It was something absurd, impossible—like teaching a wolf to sing or a boulder to float.
Demons possessed inhuman strength and regeneration. Humans, fragile in comparison, survived only through Breathing Styles and Nichirin Blades. The two were meant to oppose each other, not overlap.
And yet, the idea stirred something in him.
Could a demon truly learn a Breathing Technique?And if it could—what kind of power would it wield?
"…Perhaps," Urokodaki finally said, voice low with intrigue, "it's worth trying."
His curiosity was genuine.
A demon mastering Breathing—such a thing could change the very balance of the Corps.
After lunch, Urokodaki began to personally instruct Nezuko in Water Breathing. Since she couldn't train outside under the sun, lessons had to take place within the cabin.
Despite her unique condition, she was an eager student. She had no swordsmanship background, and her frequent drowsiness made progress slow—but her enthusiasm was pure and unshakable.
For Urokodaki, it was strangely refreshing. "It's been a long time," he murmured, "since I've had a student who listened this well."
Half a month later.
A man in a straw hat appeared at the foot of Mount Sagiri, walking with deliberate, measured steps. Inside the cabin yard, Chika and Tanjiro were in the middle of sparring when they noticed him.
"Wait," Chika said, pausing mid-swing. "Someone's coming."
"A person? Don't tell me—" Tanjiro's eyes lit up. "Could it be? Our Nichirin Blades! They're finally ready!"
The man drew closer—straw hat shading a strange mask beneath it. The resemblance to Urokodaki's mask was uncanny, though this one looked far less… dignified.
Tanjiro hurried over with a polite bow. "Excuse me! Are you the swordsmith?"
The man nodded once.
"I am Hotaru Haganezuka," he said simply—the famed swordsmith who forged Nichirin Blades for the Demon Slayer Corps. On his back, two long bundles were wrapped in white cloth.
Tanjiro's excitement was palpable. He led the man inside while Chika watched, arms crossed and eyes gleaming with anticipation.
When Haganezuka finally unwrapped the bundles, the newly forged blades rested within—gleaming with potential, awaiting their color.
"Judging from your hair and eyes," Haganezuka mused, tapping his chin, "you two must come from a family accustomed to fire. There's a good chance your blades will turn red. I can't wait to see it."
At that, Chika's brow twitched, her lips pressing tight.
Urokodaki, seated neatly nearby, added matter-of-factly, "Not necessarily. Both of them trained in Water Breathing. Blue would be more likely."
Nichirin Blades—also known as Color-Changing Swords—reflected the user's nature and breathing style. The color was influenced by temperament, lineage, and most strongly, by one's chosen Breathing Technique.
Water Breathing: Deep Blue.
Flame Breathing: Crimson Red.
Wind Breathing: Green.
Stone Breathing: Gray.
Thunder Breathing: Golden Yellow.
The moment arrived.
Tanjiro drew his blade first. Under the gaze of everyone present, the metal darkened—black as midnight.
"B-black?!"
"That's… unexpected," Urokodaki murmured.
In all of recorded Corps history, no wielder of a black Nichirin Blade had ever risen to fame—not even to the rank of Hashira. They were rare, mysterious… and often short-lived.
But Tanjiro only smiled. The black seemed to suit him somehow.
Then all eyes turned to Chika.
If her brother's blade was black, hers might follow suit—or so everyone thought.
The metal shimmered—then flooded with color.
A brilliant, crystalline blue.
The tone was pure, clear as spring water, almost luminous under the light. Urokodaki and Haganezuka both exhaled in relief. "Ah… that's normal, then. A Water user—blue makes sense."
But Chika herself was stunned.
Blue?
She stared at the blade, brows knitting. Why? Why blue?
Does this mean my connection to the Hinokami Kagura isn't strong enough? That I'm meant to walk the "proper" path of Water Breathing instead?
She gripped the hilt tighter, her reflection rippling in the azure metal.
How strange, she thought. This isn't the answer I expected at all.