"A Nichirin blade is also known as a color changing blade.
Its color changes according to the swordsman who wields it."
Mori Tekko spoke with clear pride as he carefully lifted the sword and extended it forward.
"Go on. Try holding it. See whether it fits you."
Tomioka Giyu reached out and accepted the blade. The moment his fingers wrapped around the hilt, he felt a faint warmth, as though the sword itself had acknowledged him. He adjusted his grip, steady and precise, then slowly drew the blade from its sheath.
At first, the steel remained pure white.
Then, as his breathing stabilized and his heart calmed, the blade began to change.
A clear azure hue spread from the base to the tip, deepening layer by layer until the entire sword resembled flowing seawater under sunlight.
Mori Tekko froze for a moment before letting out an astonished laugh.
"As expected of Urokodaki Sakonji's disciple. This color is truly rare. Even compared to your master, this blue is far more vivid."
Behind his tengu mask, Urokodaki Sakonji remained silent, yet the corners of his lips lifted slightly. Without needing words, he already understood what this meant. This disciple of his would not remain beneath him forever. One day, he would surpass him completely.
Giyu carefully returned the blade to its sheath and bowed toward Mori Tekko.
"It feels natural," he said honestly.
"Thank you for forging this Nichirin blade. From now on, I will entrust my life to it."
"Oh no, no need for such formality." Mori Tekko waved his hands hurriedly, his face slightly red.
"Just make sure you use it well. Go and slay many demons with it."
After escorting the swordsmith down the mountain path, Giyu turned toward the forest and spoke clearly.
"Kanzaburo."
In the next instant, a black crow descended from the sky and landed on his shoulder with practiced ease.
This was his Kasugai Crow, Kanzaburo.
"Please deliver this letter to the Master of the Demon Slayer Corps," Giyu said.
"I am counting on you."
"Hmph. Leave it to me." Kanzaburo puffed out his chest.
"This old one never fails."
With a strong flap of its wings, the crow vanished into the distance.
Urokodaki Sakonji stood behind Giyu and spoke calmly.
"The training ground you requested has been completed. You may begin whenever you wish."
Giyu turned immediately and bowed deeply.
"Thank you, Master."
Long before this, he had already discussed his intentions with Urokodaki. He did not wish to rush into missions. Instead, he wanted time. Time to grow. Time to correct every flaw before facing true battle.
Using memories from his previous life, he designed a training method that closely resembled the advanced Pillar Guidance of the future.
It included relentless physical conditioning, joint and flexibility reinforcement, high speed movement training, correction of sword forms, continuous endurance combat, and muscle strengthening under Total Concentration.
Although it could not perfectly replicate true Pillar Guidance, its greatest advantage lay in duration. One full year of uninterupted training would accumulate strength beyond what ordinary demon slayers could imagine.
The contents of the letter sent with Kanzaburo were simple. A request for one full year of secluded training.
At this stage, his presence or absence within the Demon Slayer Corps would not change much. What mattered was power.
After one year, he would personally slay fifty demons or one of the Twelve Kizuki and claim the position of Water Hashira.
This was not arrogance. It was certainty.
One month later.
The wooden sword was no longer in use.
With his Nichirin blade at his side, Tomioka Giyu arrived before the massive boulder once again.
Sabito sat atop it, legs dangling freely, a bright smile on his face.
"So you finally came," he said cheerfully.
"That sword looks good on you. Is that your Nichirin blade?"
He laughed loudly.
"Looks solid. Looks sharp. What, are you confident you can beat me now?"
Giyu returned a faint smile, his right hand resting on the hilt.
"Give it everything you have, Sabito."
Pain no longer existed.
Loss no longer weighed him down.
At this moment, only one belief remained within him.
Become stronger.
"Total Concentration."
"Water Breathing, Fourth Form. Striking Tide."
The slash surged forward like a crashing wave.
Sabito did not panic. He drew his blade smoothly and aligned the tip.
"Water Breathing, Seventh Form. Drop Ripple Thrust."
The attack was deflected perfectly. Sabito turned, sheathed his blade in one fluid motion, and followed with a horizontal slash.
Months of constant sparring had sharpened Giyu's reactions. He retreated while lowering his center of gravity, twisted his wrist, and countered immediately.
"Water Breathing, Third Form. Flowing Dance."
Continuous strikes disrupted Sabito's rhythm again and again. Instead of frustration, Sabito's smile widened.
"Good. That's right, Giyu. That is how a man fights."
With a powerful swing, Sabito forced distance between them, sliding back several steps himself.
The space between them widened.
"One last move," Sabito shouted excitedly.
"Let's settle this."
Giyu's gaze sharpened. His grip tightened. Together, they shouted.
"Water Breathing, Tenth Form. Constant Flux."
Two water dragons erupted from their blades and collided violently.
Their swords clashed again and again. The sound echoed endlessly.
Giyu regulated his breathing.
If this continued, he would lose.
Strength against strength would always favor Sabito.
Water does not oppose.
Water resolves.
When Sabito struck once more, Giyu adjusted his blade slightly. The attack dissolved effortlessly.
Sabito froze.
Azure light flashed.
Silence followed.
Sabito stood smiling, relief filling his expression.
"You've surpassed me," he said calmly.
"It's time for you to go."
"Take my place. Slay more demons."
Giyu nodded. No words were needed.
As Sabito faded away, Giyu watched silently.
Wait for me.
I will avenge everyone.
He turned and walked toward the training ground once more.
A full year passed.
Total Concentration Constant was mastered only one month after that battle.
Even Giyu himself found his growth unbelievable.
Perhaps it was talent.
Perhaps memory.
Perhaps Sabito's blessing.
One morning, before Giyu could speak, Urokodaki Sakonji said quietly.
"Come and sit."
"You have worked hard. It is time to leave."
He produced a pair of scissors.
"Your hair has grown too long."
"Please cut it for me, Master," Giyu said.
"I do not know when I will return."
Urokodaki nodded and draped a white cloth over him.
As he cut, he spoke of breathing, demons, and resolve.
When he finished, he handed over a pieced haori.
"Carry their will," he said softly.
"Walk your path without hesitation."
Giyu bowed deeply.
"Thank you, Master."
And with that, Tomioka Giyu stepped forward toward his destiny.