Shinobu's Sorrow and Armament Haki

At night, moonlight poured over the Butterfly Mansion like liquid silver, bathing the courtyard in a cool glow. The bustle of the day had long since faded, leaving only the chirping of summer insects and the faint sound of wind in the distance.

Moyu had finished a day of training and was about to return to his room when his Six Eyes caught a slender figure on the roof.

It was Shinobu Kocho.

She sat alone on the roof ridge, her arms wrapped around her knees as she gazed up at the crescent moon on the horizon. Moonlight traced her slender profile. The gentle smile she always wore had vanished, replaced by an indescribable loneliness and... sorrow. The night breeze stirred the loose strands of hair at her temples and her butterfly hair ornament, making her look especially fragile.

Moyu paused, then leaped lightly onto the tiles beside her, landing without a sound.

Shinobu did not seem surprised by his arrival. Without turning around, she spoke softly, her voice carrying a distant note that was not usually there. "Oh, it's you, Moyu. The moon is beautiful tonight, isn't it?"

"Mm." Moyu sat down beside her without saying anything more. He could "see" the subtle fluctuations in her aura: a pain buried deep in her heart, wrapped beneath layer upon layer of smiles.

The two sat in silence for a while, with only the wind passing by.

"Moyu," Shinobu said softly, her gaze still fixed on the moon, "sometimes I feel like time passes so quickly. In the blink of an eye, it's already been... so long since my sister left."

Moyu's heart sank slightly. He knew who she meant: the former Flower Hashira, Kanae Kocho. That gentle, kind woman who had dreamed of humans and demons living together in peace had ultimately died a terrible death at the hands of Upper Rank Two, Doma.

"My sister Kanae... was a very, very gentle person." Shinobu's voice was faint, as if she were afraid of disturbing her memories. "She always believed there were demons in this world who didn't hurt people, and hoped that one day we could live together in peace... She was so naive it was endearing, wasn't she?"

The corners of her mouth curved into the faintest, bitterest smile.

"But reality is always so cruel." Her voice fell, carrying a barely perceptible tremor. "And the one who took her life just had to be... a thoroughly evil demon who takes pleasure in other people's suffering."

Moyu could feel the bone-deep hatred and killing intent suppressed beneath her calm tone as she said "evil demon." That hatred was the driving force she hid behind her smile every day, and also the shackle that bound her firmly to the past.

"Miss Shinobu," Moyu said suddenly, his voice calm but clear, "I can understand your pain and sorrow. Even though we haven't known each other long, for some reason, I always feel like I've known you for a long time."

Shinobu froze slightly and finally turned to look at him, a questioning light flickering in her violet eyes in the moonlight.

Moyu met her gaze, his azure eyes deep as the sea, and continued, "If I get the chance, I'll kill Doma for you."

The air froze.

The expression on Shinobu Kocho's face went completely rigid. Her pupils contracted sharply, her eyes filled with incredulous shock! Doma! How could he know that name?! She had never told anyone the identity of the demon who killed her sister, apart from Oyakata-sama and a very few core members! Even most of the other Hashira only knew it had been an Upper Rank demon, not which one!

"You..." Shinobu's voice carried a barely perceptible tremor as she stared intently into Moyu's eyes, which seemed capable of seeing through everything. "How did you... Oh, right, your eyes... They really are remarkable." In the end, she attributed it to Moyu's mysterious "Six Eyes," thinking he had seen something that happened in the past.

Moyu did not explain. He simply said calmly, "When that time comes, Miss Shinobu, perhaps you can... truly be yourself again."

Be herself again? The Shinobu Kocho who, under her sister's protection, could be shy, could get angry, and could have the dreams of an ordinary girl, rather than the Insect Hashira she was now, who disguised her pain with a smile and turned herself into a poisoned blade?

Shinobu was silent for a long time. In the moonlight, the lines of her profile seemed to soften somewhat. She turned back toward the distant moon and sighed softly, her voice barely audible. "Be myself again... you say? I've almost forgotten what that version of me was even like..."

She neither admitted nor denied it, but those words were themselves a kind of tacit admission and... a faint hope that even she did not dare touch.

The two fell silent again, but the atmosphere was no longer so heavy. Instead, there was a trace of unspoken rapport and understanding between them.

In the days that followed, training at the Butterfly Mansion continued in full swing.

Tanjiro had gained a basic grasp of the Breathing Style technique Total Concentration: Constant and had begun practicing to solidify it, working to make that breathing state instinctive.

Zenitsu and Inosuke, meanwhile, were still struggling with Constant. Zenitsu always complained that maintaining Total Concentration Breathing was too exhausting and slacked off after only a few minutes, only to be spurred back to his feet by Aoi telling him, "If you keep this up, no girl will ever like you." Inosuke still forced his way through with brute strength, frequently getting a stitch and howling in pain, but once he was done howling, he stubbornly continued.

During a break in training that day, Moyu gathered Tanjiro, Zenitsu, Inosuke, Kanao Tsuyuri, and Shinobu Kocho together.

"I've recently worked out a technique for using energy that might help improve your strength," Moyu said, getting straight to the point. "It's called 'Armament Haki.'"

"Armament Haki?" Tanjiro repeated curiously.

"Haki? What's that? Can you eat it?" Inosuke yelled.

Zenitsu's eyes lit up. "It sounds really powerful! Will learning it make me more popular with girls?"

Moyu ignored their antics and began to explain. "It's a kind of energy hidden deep within the body. By guiding its flow with your will in a particular way, you can coat your body or a weapon with it, greatly increasing defense and attack power. It can even touch certain physical forms that ordinary physical attacks have trouble affecting, such as... certain special Blood Demon Art creations, or a demon's actual body."

That last sentence made everyone present turn serious. The ability to directly increase their power to kill demons was immensely significant.

"Learning Haki requires a strong physique and a firm will as a foundation." Moyu swept his gaze over them. "Tanjiro has already grasped the basics of Constant, and his physique is improving rapidly. Miss Shinobu is a Hashira, so there's no question about her foundation. Kanao has a very good foundation. As for Zenitsu and Inosuke..."

He paused. "Although you two haven't fully mastered Constant yet, your physiques are still much stronger than those of ordinary Corps members. You can try sensing it, but don't rush for results, or you might hurt yourselves."

Over the next few days, Moyu began giving them detailed instruction on how to train Haki: how to sense the energy flowing within their bodies, how to use their will to guide it together, and how to coat specific parts of their bodies with it...

The process was not easy. Unlike Breathing Styles, Haki placed greater emphasis on combining and controlling "will" and "energy."

Tanjiro studied diligently, but he struggled somewhat with this use of energy, which required extremely precise control. His progress was slow; he would often manage, with great difficulty, to form a thin black film on his palm, only for it to dissipate within seconds.

Zenitsu tried to use his extraordinary hearing to "listen" to the flow of energy within his body, but he could hear nothing except his own heartbeat and the rush of blood, leaving him scratching at his head in frustration. Inosuke relied entirely on his beastly instincts, driving his energy at random. He either failed to produce a damn thing or sent the energy out of control, leaving his arm numb and earning him a stern scolding from Aoi.

Kanao remained silent, but she was exceptionally gifted and had astonishing powers of concentration. Under Moyu's instruction, she was the quickest after Shinobu to sense the energy, and she could already form a faint but stable black sheen on her fingertips.

The one who progressed fastest, naturally, was Shinobu Kocho.

She was a Hashira to begin with, and her control over her body and her willpower far surpassed the others'. With Moyu's special explanations and guidance, she took only three days to successfully coat her entire palm in Armament Haki. The black layer was not deep in color, but it was even and stable, with a metallic texture.

Shinobu looked curiously at her blackened palm and tapped it lightly with a finger. It gave a soft knock, and its hardness had clearly increased. She then drew her Nichirin Blade and tried to coat it in Haki. At first, she could only cover a small portion of the tip, and even that was very unstable. But under Moyu's guidance, she kept adjusting the coordination of her breathing and will, gradually becoming able to maintain a stable Haki coating over the front half of the blade.

"What a wondrous power..." Shinobu felt the solid, contained power coming from the blade, her violet eyes sparkling. "It feels like the blade has become much sharper and tougher. If I used it for a thrust..."

She casually thrust at a thick wooden training board beside her.

"Shhk!"

Without using any Breathing Style form, she delivered the most ordinary of straight thrusts. The Haki-coated tip pierced the board as easily as a hot knife through butter, leaving an utterly smooth cut.

"Amazing!" Tanjiro exclaimed.

"Wow! Miss Shinobu, you're so strong!" Zenitsu's eyes were full of envy.

"Tch, I'll be able to do that soon enough!" Inosuke huffed, unwilling to admit defeat.

"Moyu," Shinobu said, looking at him with a serious expression, "this 'Armament Haki' is tremendously important. I was wondering... could I report it to Oyakata-sama and teach it to the other Hashira, and even the members of the Demon Slayer Corps? It could greatly improve everyone's overall survivability and fighting strength." She paused, then added, "Of course, you developed this technique, so we must have your permission."

Moyu had expected this and nodded calmly. "Yes. After all, the stronger the people of the Demon Slayer Corps are, the greater their chances of surviving battles with demons. Besides, the other Hashira all have strong physiques, so they should learn it faster than Tanjiro and the others. They can master it first, then teach it to the ordinary Corps members."

Shinobu looked deeply at Moyu, her eyes full of gratitude. "Thank you, Moyu."

Before long, Kagaya Ubuyashiki received Shinobu's report. The Master naturally gave his full support to a new technique that could significantly increase their strength. He personally summoned Moyu to express his thanks and ordered Moyu and Shinobu, who had already gained a basic grasp of it, to jointly teach the Hashira how to train Armament Haki.

All ten Hashira gathered, and the other Hashira reacted in different ways when they learned of the new technique.

Kyojuro Rengoku spoke in a booming voice. "Mm! Eye Hashira, you are truly remarkable!"

Gyomei Himejima softly chanted a Buddhist prayer. "Namu... Thank you for sharing this so selflessly."

Tengen Uzui laughed flamboyantly. "Hahaha! Such a flamboyant power! It suits me perfectly!"

Mitsuri Kanroji blushed and thanked him quietly. "Th-thank you, Mr. Eye Hashira..." Mr. Eye Hashira seems quite handsome too.

Muichiro Tokito tilted his head, seemingly trying hard to understand.

Obanai Iguro nodded silently.

Giyu Tomioka: "..."

Although Sanemi Shinazugawa still felt a little awkward around Moyu, faced with a chance to grow stronger, he merely snorted and set about training hard.

The Hashira's physiques and talents were indeed extraordinary, and under Moyu and Shinobu's guidance, they progressed rapidly. In less than half a month, most of the Hashira had mastered the basic coating technique and begun moving on to the more advanced "wrapping." The overall strength of the Demon Slayer Corps quietly reached a new level.