Poison in her palms. 　Even knowing that, the Demon Slayer Corps soldiers stood in formation before her, their faces serious. 　The training grounds at dusk. Afternoon sunlight streamed diagonally across the wooden floor, casting long shadows of a dozen young swordsmen. 　Kochou Shinobu stood before them. 　She was not tall. Her slender frame was dressed in a wisteria-colored kimono with a white haori. On the back of the haori, a purple butterfly was embroidered, glimmering faintly in the setting sun. The tips of her black short hair were dyed a pale wisteria color, blending naturally with her kimono. Her deep brown eyes were calm, yet held a hidden sharpness. A small butterfly tattoo peeked from the gap in her haori near her left shoulder. 　At her waist hung a thin sword. A Nichirin blade—the only weapon capable of killing demons, forged from scarlet ore. But Shinobu's blade was different from a standard Nichirin sword. It was specialized for thrusting: thin and long. Inside the scabbard was a mechanism that released poison the moment the blade pierced flesh. "Demons, you see," 　Shinobu spoke gently. "[gentle]won't die unless you sever their necks with a Nichirin blade. And sunlight. That's why we must finish them before dawn breaks." 　One of the soldiers was taking notes. A newcomer, probably—his hands trembled slightly. 　Shinobu turned her gaze toward him and smiled softly. "[gentle]You don't need to be nervous. Today isn't about learning—it's about watching." 　The newcomer flinched and looked up, then relaxed his shoulders a little. 　This was the tenth day of Pillar Training. A special regimen where the "Pillars"—the highest-ranking swordsmen of the Demon Slayer Corps—trained the lower-ranked soldiers in rotation. It had been decided by Ubuyashiki Kagaya, the head of the Ubuyashiki clan, whom all soldiers called "Master," in preparation for the coming final battle. This was Shinobu's third day of instruction. "Lady Shinobu," 　One soldier raised his hand. A tall swordsman. "[serious]Your blade, Lady Shinobu... you can't sever a demon's neck with it, can you?" 　His tone was hesitant. His face showed he worried he'd said something rude. 　Shinobu saw this and chuckled. "[gentle]That's right. I don't have the arm strength to sever a demon's neck." 　She admitted it plainly. 　The soldiers stirred. "[gentle]So I use poison instead." 　Shinobu drew her blade smoothly. The thin blade reflected the setting sun and gleamed. She stepped forward and thrust it into a wooden pillar. 　Fast. Too fast to follow with the eye. 　The moment the blade pierced the pillar, a faint sound of liquid flowing could be heard. "The Insect Breathing—a fighting style I developed myself. Sword techniques specialized for thrusting, combined with poison made from wisteria flowers. Through Total Concentration Breathing, I raise the oxygen in my body and boost my physical abilities to a level where I can fight demons. Without it, someone with my build would be killed before even getting close to a demon." 　She showed them the tip of the drawn blade. A thin layer of purple liquid glistened on the steel. "Wisteria flower poison. The one thing demons truly despise. I can switch between different types while fighting. I change the composition to match my opponent's strength." 　The soldiers leaned forward. Gasps of admiration rose. The newcomer who'd been taking notes stopped his pencil and stared intently at Shinobu's blade. 　Shinobu sheathed her sword and returned to her calm smile. 　For the next hour, she continued with the fundamentals. The mechanics of Total Concentration Breathing, demon regeneration abilities, the differences between Upper and Lower Moons. Shinobu explained each point carefully and clearly. 　As the sun sank lower and the training grounds turned orange, the lesson ended. 　The soldiers filed out. 　The last one bowed deeply with a loud "Thank you very much!" and disappeared beyond the gate. 　Footsteps faded into the distance. 　Fading away. 　Fading away. 　Silence fell. 　Shinobu's smile vanished in an instant. 　The empty training grounds. Alone on the wooden floor, Shinobu stood like a different person. The gentleness was gone, replaced by an expression that gazed toward some distant place. 　She raised her hand and gently touched the hair ornament pinned in her hair. 　A small butterfly decoration. The wisteria-colored one was a keepsake from her sister, Kochou Kanae, who had died four years ago. 　Kanae had been a former Flower Pillar. A person who had genuinely wanted to "befriend demons." She was kind, warm, and fought until just before dawn broke, until her strength gave out. Killed by Douma, Upper Moon Two. A demon who had laughed while devouring her sister. 　Shinobu gripped the hair ornament and whispered in her heart. （Sister. Am I doing this right?） 　No answer came. Of course not. 　Shinobu remained still for a moment, then lowered her hand. 　The path back to the Butterfly Mansion wound through narrow mountain trails. 　Dusk had ended, and the sky was turning indigo. Small flowers bloomed along the roadside, swaying with each breeze. Shinobu glanced at one for a moment, then looked ahead again. What kind of flower was that? she wondered, but forgot immediately. 　A rustling sound. 　A black shadow plummeted from the sky and landed on Shinobu's shoulder. 　A Kasugai Crow—a special raven used by the Demon Slayer Corps for communication, capable of understanding human speech. Each soldier was assigned one, and they delivered messages from the Ubuyashiki household verbally. Shinobu's crow was restless, shifting its feet on her shoulder. "[excited]Message from Master Ubuyashiki! Demon sightings have surged in the mountainous regions! Eight people have gone missing from three villages in the past ten days! Alert status should be maintained alongside Pillar Training!" 　It delivered the entire message in one breathless rush. 　Shinobu stopped walking. Eight people. In ten days. 　The crow spread its wings and flew off, having completed its task. A single feather drifted down onto her shoulder. Shinobu watched it, then looked ahead. 　Her walking pace quickened. 　The first thing she did upon returning to the Butterfly Mansion was head straight to the compounding room. 　Opening the door, the dry scent of wisteria flowers greeted her. Dozens of medicine bottles lined the shelves, and a distillation apparatus sat in the corner. The compounding room was off-limits to regular soldiers. Shinobu's place alone. 　She checked her inventory. Wisteria flower poison—the standard concentration for ordinary demons. That was sufficient. 　The problem was the supply for Upper Moons. 　Upper Moon demons could sometimes break down poison within their bodies. So it had to be refined many times more concentrated than usual. That stock—was low. Nowhere near enough. （Another all-nighter, then.） 　Shinobu pulled out a chair and sat. The thought of asking someone for help never crossed her mind. Having Aoi assist her, or asking Kanao to do something—such ideas never occurred to her from the start. She would do it herself. That was normal for Shinobu. 　She began her work. 　Night deepened. 　The distillation apparatus quietly released steam. Outside the window was pitch black, with only the sound of insects. Shinobu processed wisteria flowers one by one, carefully. She crushed the dried petals, extracted the components, and increased the concentration. 　Simple work. But it required focus. 　After a while, her hands stopped. 　Crushed wisteria petals lay in her palm. That purple color—overlapped with something in her memory. 　A smile. A smile that killed people. 　Douma's face surfaced in her mind. 　Upper Moon Two. The demon who killed her sister. Shinobu didn't know what his face looked like. But she could imagine it. He must have smiled happily, joyfully, as he devoured her sister. She knew what kind of demon he was. 　Anger seeped into her hands. 　Before she realized it, she was clenching her fist. 　A wet crunch. The wisteria flowers crushed to pulp. 　Flower petals stained her palm purple. 　Shinobu didn't move for a while. 　Then she took a deep breath. Once. Twice. 　A small mirror hung on the wall. For checking if any compounds had splashed on her face during work. Shinobu looked at her reflection. 　She crafted a smile. 　Her usual, gentle smile. 　She made it perfectly. That perfection felt hollow. （It might not work on Upper Moons.） 　That thought lingered. The possibility that poison could be broken down. The limits of her fighting style. Shinobu had carried this fact all along. She'd never told anyone. She fought with a smile, returned with a smile. That was all she'd done. 　She discarded the crushed wisteria flowers and took out fresh ones. 　She resumed her work. 　Just before dawn, a sound came from outside. 　Shinobu stopped. Footsteps. Light ones. The Hidden—the Demon Slayer Corps' support unit. They didn't fight, but delivered information and transported the wounded. They sometimes came to the Butterfly Mansion like this. 　She opened the door. A figure in black garments stood there, half their face hidden by cloth—dressed as one of the Hidden. "[serious]I've come to report. The damage in the mountainous regions has expanded further. Last night, another person went missing near Hiiragi Village—" 　Shinobu didn't wait for the report to finish. 　She was already standing. 　Her mind calculated. If she left now, she had half a day before the next Pillar Training assignment. To Hiiragi Village's direction, it wouldn't take two hours if she hurried. Go, confirm the situation, return. Possible. "Understood." 　She said it curtly and returned to the compounding room. She checked her spare poison needles. Enough. The poison in her sword's scabbard had just been refilled. Packing took no time. 　She didn't think to tell anyone. Contact Giyuu? Call the other Pillars? The thought barely formed before it vanished. She could handle it herself. It wasn't something that required involving others. 　Besides, Shinobu rarely communicated that way. 　As she stepped outside, the eastern sky was just beginning to lighten. The darkest hour before dawn. The scent of wisteria flowers drifted faintly. The barrier surrounding the Butterfly Mansion—a wisteria-flower mechanism that kept demons out. "Lady Shinobu?" 　A voice called. She turned to see one of the three young girls—Kiyo—standing in the hallway. Her eyes were sleepy. Had she woken early, or had she been awake all night? "[gentle]I'm just stepping out for a bit. I'll be back soon." 　Shinobu turned back and crafted a smile. "[gentle]Please prepare lunch for us, will you?" 　Kiyo answered cheerfully, "Yes!" A response without doubt, straightforward and pure. 　Shinobu walked toward the gate. 　That smile was too perfect. Kiyo couldn't worry about anything. 　Once Shinobu entered the mountain path, her expression changed again. 　No one was watching. No eyes upon her. So she didn't need to smile. 　She moved quickly between the trees. Morning dew wet the grass, making soft sounds with each step. The sky slowly brightened. A bird called somewhere in the distance. 　Shinobu walked forward, her gaze fixed ahead. 　Her back looked, just a little, lonely.