A Different Kind of Red Nichirin Blade

Over the next few days, the Butterfly Mansion returned to its usual peace and routine, though without the commotion of Tanjiro and his two companions. Moyu devoted most of his time to training.

He already understood the principles behind the Red Nichirin Blade. The key was to efficiently channel and stabilize "heat" containing the power of a Breathing Style and his own will within a Nichirin Blade. For others, that might have required repeated experimentation, sudden enlightenment, or even an emotional outburst, but to Moyu, with his Six Eyes, it was more like solving a complex problem involving energy conduction and thermodynamics.

In the courtyard one morning, before the dew had dried, Moyu stood alone in an open space with the Azure Star in his hand. Rather than rush to exert himself, he slowly closed his eyes—not truly shutting off his vision, but drawing the perception of his Six Eyes completely inward, focusing it on the small area where his palm met the hilt and on the microscopic structure inside the blade.

In his vision, the blade was no longer cold metal, but a complex network of countless fine energy pathways. These pathways were the foundation of the "life" the swordsmith had given the blade during forging, as well as channels that resonated with its wielder's Breathing Style. His own Breathing Style's cursed energy flowed slowly along them like an azure stream.

Heat... is energy moving violently, at its core. The realization came to Moyu. Instead of letting his Breathing Style energy flow smoothly, he tried making it oscillate and rub at high speed at certain key nodes inside the blade, following a specific frequency and path.

Hum...

The Azure Star's blade began to tremble gently, emitting a faint hum. The metal near the guard took on a faint dark red hue at a speed visible to the naked eye, as though warmed by embers!

It worked! But after less than three seconds, the dark red quickly faded, and the blade grew cold again. His choice of energy oscillation nodes had not been precise enough, and he had failed to maintain a stable frequency. The energy consumption was still acceptable.

Moyu was not discouraged. The powerful insight and analytical ability of his Six Eyes came into play. The path of the energy flow during those three seconds, the distribution of heat, the reason it had dissipated... all the data was recorded and analyzed in an instant. He adjusted the rhythm of his breathing and tried again.

This time, the nodes of energy oscillation were more concentrated, and the path was better optimized. The humming of the trembling blade grew a little sharper, the dark red area extended an inch or so forward from the base of the blade, and the color grew slightly brighter. It lasted five seconds.

Failure, analysis, adjustment, another attempt.

Day after day, Moyu refined the process of channeling energy like a master craftsman working with the utmost precision. In a corner of the courtyard, the hardwood stake used for testing gradually accumulated slash marks of varying depths, their edges faintly scorched. They were marks left when the Red Nichirin Blade's state was unstable.

His progress was visible to the naked eye. From the initial three seconds of redness near the guard, he progressed to maintaining a pale red color across nearly half the blade for more than ten seconds, then to attempting to activate the Red Nichirin Blade at the instant he swung and maintain it throughout the entire attack...

Five days later, in the early morning.

Moyu calmed his mind and breathed long and steadily. His right hand held the sword with a firm, steady grip. At a thought, his Breathing Style energy, refined through countless adjustments, surged instantly along its designated pathways like a lit fuse!

Swish!

The Azure Star's blade abruptly lit up with a steady, brilliant crimson from guard to tip! It did not flicker like a flame, but gave off the subdued red glow of searing metal buried deep underground and tempered through countless hammer blows! The heat distorted the surrounding air with faint crackles, and a wave of heat spread out from the blade.

He swung it gently forward, not at the wooden stake, but through the air. A crimson trail lingered for an instant, as though it had cut a scorching fissure through the morning light itself.

"It's done." Moyu slowly let out a breath. The crimson receded from the blade like a tide, returning it to its original azure flowing-water pattern. Though he was still some way from controlling it as naturally as his own arm or maintaining it for a long time, there was no doubt he had mastered the basics. He could even feel that, in its Red Nichirin Blade state, the Azure Star was more closely connected to him and conducted cursed energy a little more smoothly.

"My, what astonishing progress, Moyu," a gentle voice said from beneath the veranda, tinged with admiration.

Moyu sheathed his blade and turned to look. Shinobu Kocho had appeared there at some point, dressed in ordinary clothes with her butterfly-patterned haori draped loosely over them. She held a steaming cup of medicinal tea and watched him with a smile, the light of the courtyard reflected in her purple eyes. Clearly, she had been watching for a while.

"I only figured out the principles and practiced," Moyu said. He walked over to the veranda and accepted another cup of tea from her. The tea was just the right temperature, carrying the delicate fragrance of chamomile and some kind of calming herb.

"The principles..." Shinobu Kocho took a small sip of tea, her gaze settling on the Azure Star at his waist. "Making a Nichirin Blade stay red isn't something you can do just by 'figuring out the principles.' Especially you, Moyu. You don't seem to have relied on an intense emotional outburst or on extreme grip strength or collisions." She had observed him closely.

"Yes, I took a shortcut. I used energy control to replace some of the external force required," Moyu admitted. His method placed greater emphasis on internal energy conversion and precise control. It made relatively lower demands on sheer physical explosiveness, but required extremely precise energy control, which was why others would find it difficult to replicate.

"So it really does have something to do with your eyes?" Shinobu Kocho said thoughtfully. "Then could someone with weak wrists like me learn anything from this 'shortcut'?"

She asked directly, also making her own predicament clear. As the Insect Hashira, Shinobu Kocho excelled at speed and poisons, and wrist strength was indeed her weakness. It was also why she had chosen to have a rapier-like Nichirin Blade forged. The traditional methods of activating a Red Nichirin Blade were even more difficult for her.

Moyu looked at her. Shinobu Kocho was looking back at him, her purple eyes clear and earnestly inquisitive, with a trace of barely perceptible anticipation. He knew she was not pursuing absolute killing power in a direct confrontation, but the Red Nichirin Blade's ability to suppress a Demon's regeneration would undoubtedly be a tremendous advantage for her fighting style, which specialized in inflicting wounds and injecting poison—it could make the poison take effect faster, or make it harder for a Demon to repair poisoned tissue.

"In theory, it's possible." Moyu pondered for a moment. "Your Breathing Style energy has unusual properties, tending toward penetration and destruction. If you can stimulate it inside the blade at a specific frequency to produce enough heat... But we'll have to experiment to see exactly how to combine it with your Insect Breathing. My method can only serve as a reference."

"Having something to reference is already wonderful." Shinobu Kocho's smile grew brighter. "Then, Teacher Moyu, do you have time to give your student some guidance?"

She used the title "teacher" partly in jest, but it also showed her willingness to learn from him.

Moyu nodded. "We can start now."

The two went to the center of the courtyard. Shinobu Kocho took off her Nichirin Blade. Like its owner, the blade was slender and light, with a faint purple sheen like a butterfly's wing.

"First, you need to fully perceive your blade." Moyu stood beside her and gestured for her to hold it. "Don't look with your eyes. Use your breathing and your will to 'feel' the pathways in the blade, as though it were an extension of your own arm."

Shinobu Kocho closed her eyes as instructed and adjusted her breathing. The light, subtly trembling rhythm unique to Insect Breathing sounded. Her perceptiveness was already excellent, and she soon immersed herself in it.

Moyu's Six Eyes took in both her and the blade. In his vision, Shinobu Kocho's Breathing Style energy was a peculiar pale purple, like drifting powder, with strong nerve-numbing and cell-destroying properties. The energy was trying to establish a connection with the relatively slender energy pathways inside the blade.

"Can you feel them? Those 'channels,'" Moyu prompted softly.

"Mm... They're very faint, and they're a little... out of sync with my breathing?" Shinobu Kocho frowned slightly.

"That's because your energy tends toward penetration and dispersal, while the blade's pathways need concentration and oscillation to generate heat." Moyu went straight to the heart of the problem. "Try changing the way you release your energy. Don't think about covering the blade evenly. Instead, imagine concentrating the energy into extremely fine needles and repeatedly piercing back and forth at high frequency along a few of the main pathways."

It was an unconventional approach based on the insight of his Six Eyes.

Shinobu Kocho tried it. At first, the pale purple energy remained scattered. But under Moyu's precise verbal guidance, she gradually got a feel for it. Fine streams of highly concentrated purple energy began darting rapidly through the blade.

The blade grew slightly warm.

"It's working!" Shinobu Kocho opened her eyes, a flash of delight in their purple depths. Though the temperature was still far from that of a Red Nichirin Blade, it proved they were on the right track.

"But it consumes a lot of energy this way, and the heat is uneven," Moyu pointed out. "Next, try controlling the rhythm of those 'needles' so they collide or turn simultaneously at specific nodes. Use the instantaneous friction and energy conversion to generate more heat. Remember the locations of the nodes. I'll show you."

He extended his right index finger, its tip surrounded by an extremely faint azure glow, and lightly pointed just above different spots on the Nichirin Blade in Shinobu Kocho's hand.

"Here, and here, are key intersections for the flow of energy. Here is the area where the blade's structure is best suited to retaining heat..."

His fingertip never actually touched the blade, but his precision and certainty left Shinobu Kocho without doubt. She concentrated on memorizing the locations while adjusting the flow of energy through her body.

Time passed bit by bit. All that remained in the courtyard was the sound of Shinobu Kocho's breathing, sometimes slow and sometimes rapid, and the occasional faint hum from her Nichirin Blade, a little lower than before.

Sweat dampened the loose strands of hair on Shinobu Kocho's forehead, but her gaze remained focused, her purple eyes fixed on the blade as she continued to try and adjust. Training to use a Red Nichirin Blade was clearly no easy task, especially for someone like her who was attempting to take the path of precise control.

Moyu watched quietly from the side, occasionally pointing out the key issue in a few concise words when her energy flow noticeably faltered or went in the wrong direction.

Finally, after she had lost count of how many dozens of attempts she had made—

Hiss—

A faint purplish-red sheen spread for about two inches along Shinobu Kocho's slender Nichirin Blade, starting near the guard! The color was not as blazing as Moyu's crimson, tending more toward a scorching deep purple, but the heat it radiated was unmistakable. Even the hand she held the hilt with felt its warmth clearly.

It was only two inches, the color was faint, and it lasted only a brief instant before dissipating.

Yet a smile of relief and accomplishment appeared on Shinobu Kocho's face, far brighter and more vivid than the gentle smile she habitually wore. She let out a soft breath and shook her somewhat sore and numb wrist.

"I did it... the first step." She looked at Moyu, her eyes shining. "There's still a long way to go, but at least I can see that it's possible."

"Getting started is the hardest step. Now that you have a direction, what comes next is practice and refinement," Moyu said objectively. "Your energy has unusual properties, so the 'Red Nichirin Blade' state you eventually achieve may differ from the usual one. Its effects might be more suited to suppressing regeneration and helping poison penetrate."

"That would be better than I could have hoped for." Shinobu Kocho carefully sheathed her blade and wiped the sweat from her temple with her sleeve. Her tone returned to its usual gentleness, but the smile in her eyes was genuine and warm. "Thank you, Moyu. That was very... precise guidance."

"We learned from each other," Moyu said mildly. He had indeed gained some inspiration from Shinobu Kocho's way of controlling energy. Perhaps the delicate, meticulous penetration of Insect Breathing could be applied to the Reverse Cursed Technique or to more intricate uses of energy.

The setting sun stretched their shadows long. In the courtyard, one continued to ponder how to stabilize and unleash the Red Nichirin Blade, while the other repeatedly practiced the purplish-red blade glow that had only just begun to take shape. The air was filled with the scent of herbs, the faint smell of heated metal, and an unspoken understanding between them as they progressed together.

Daily life at the Butterfly Mansion continued steadily amid such focused training and occasional conversations.