Dawn broke, but Shinobu did not leave the preparation room. The old woman's trembling words from the previous night refused to leave her mind. A demon that laughed while devouring people. That voice lingered in her ears still. ——There's no choice but to do this. Shinobu stared at the medicine bottles lined up on the desk. The conventional concentration of wisteria flower poison would not work against demons near the Upper Moons. It would be broken down inside their bodies. That's why she needed to concentrate it threefold. The logic was sound. The problem was that increasing the concentration made the poison's components unstable. She applied heat with the distiller. Carefully adjusted the concentration. Transferred it to a bottle. After a while, the liquid in the bottle began to bubble. The liquid started to separate. A failure. "……Again." She sighed and set the bottle aside. Failed batches—four, five of them—lined up in a row. Pushed to the edge of the desk as if cornered. When the sun climbed higher, she sensed a presence in the hallway. Without turning around, Shinobu spoke. "[serious]Aoi, you don't need to help right now. This work must be done alone." There was no response. Thinking something was odd, she turned around. A figure stood leaning against the pillar in the hallway. Black hair with blue streaks mixed in. Cold, deep blue eyes that stared intently at Shinobu's hands. It was Tomioka Giyuu. "[surprised]……Tomioka-san. What are you doing here?" Giyuu paused for a moment. "If you collapse, it would be troublesome." That was all he said, then fell silent again. Shinobu lost her words for an instant. She hadn't expected such a response. Such an awkward way of putting it. Yet somehow, something in her chest loosened. A genuine smile escaped—not a manufactured one. "[gentle]I see. Then please, watch as much as you like from there." Giyuu nodded silently. He remained leaning against the pillar in the hallway, unmoving. Shinobu resumed her experiment. She adjusted the distiller, carefully mixed the components, and transferred them to a bottle again. Bubble. The liquid bubbled. Separating again. "……Another failure." Giyuu watched intently. He said nothing. He did nothing. He was simply there. For some reason, that made it slightly easier. It was past midday, when the afternoon light began to slant through the preparation room's window. A rustling sound came from the garden. Followed by a sharp bird's cry. "[excited]Urgent message from Lord Ubuyashiki! The Kuromatsutsu settlement in the mountains has suffered a large-scale demon attack! A house with the wisteria flower crest—half-destroyed! Confirmed deaths of elderly cooperators! Immediate deployment requested!" A Kasugai Crow—a special raven that understood human speech and handled communications for the Demon Slayer Corps. Its shrill voice echoed through the Butterfly Mansion. Shinobu's hands stopped. A house with the wisteria flower crest. Those were the homes of cooperators who had provided lodging, meals, and medical treatment to the Demon Slayer Corps without charge. A place passed down through generations by clans who had once been saved by the Corps. That house had been directly targeted. ——This isn't just a random appearance. When Shinobu glanced toward the hallway, Giyuu was already standing. His hand rested on the hilt of his Nichirin sword. Their eyes met. No words were exchanged. "[serious]I'll prepare portable poison. Please wait a moment." She moved swiftly. She retrieved the experimental poison bottle that had been in the middle of preparation. The threefold concentration—still unstable. The best of the failed batches, sitting beside the others. (I really don't want to use this. But I can't leave without it.) As she packed it into a portable leather pouch, Giyuu spoke curtly. "I'll take the front. You strike with poison from the flank." "Understood." That was the extent of their coordination. The two burst out of the Butterfly Mansion. They ran along the mountain path. The sky approaching dusk was orange, and the shadows of trees stretched long. Giyuu's pace was fast. Shinobu kept pace beside him, using Total Concentration Breathing. The sensation of blood flowing surged through her entire body. There were few words. But the air was slightly different from the previous night's mountain path. The night before, they had walked while probing each other. Now it was different. They faced the same direction. They arrived at Kuromatsutsu settlement when the sky had turned completely dark. Smoke was visible in the distance. As they drew closer, the smell of char grew stronger. The sound of burning wood. The sound of collapse. And——the smell of blood. At the settlement's entrance, several houses were still burning. "[serious]Search for survivors." Giyuu rushed forward. Shinobu followed. They circled the burning houses, ran through alleys. Even in the darkness, moonlight and firelight illuminated their feet. In the shadow of a collapsed house, Shinobu found a small figure. She crouched to check. A child. A boy, perhaps ten years old. Unconscious. She immediately checked for a pulse. It was there. Breathing too. There were external injuries, but nothing deep. He was simply knocked out. (Thank goodness.) As she pulled out cloth for first aid and began treatment quickly, wrapping and securing—— In that instant, the ground rumbled behind her. A cracking sound. No—the sound of earth freezing. She turned around. About ten meters away, a demon stood. Clearly not a Lower Moon. Its build was larger, its posture too still. It wasn't thrashing about like a beast. It was looking at them——as if appraising them. The air around them changed. White mist began to drift. The temperature dropped suddenly. Frost formed on the ground. ——Blood Demon Art. "Fall back." A low voice. Before she knew it, Giyuu was standing in front of Shinobu. At the same time, he grabbed her arm and pulled her backward. With strong, swift force. Shinobu was drawn back. Giyuu's hand touched her arm. ——His hand was cold. But that hand was somehow warm. Calloused from the sword, scarred, yet it had strength in its grip. (Why would he……) For just a moment, she thought something strange. She quickly refocused. This was combat now. Giyuu drew his Nichirin sword. Water Breathing——the most widely practiced style among Total Concentration Breathing techniques. Characterized by excellent offensive and defensive balance, smooth and flexible swordwork. Giyuu had mastered it as a Water Hashira. The demon moved. Fast. It closed the distance to Giyuu at a speed incomparable to Lower Moons. Giyuu's blade met it. A metallic clang rang out across the night mountain. Shinobu immediately circled to the side. She took the stance of Insect Breathing. Her blade was laced with poison——a mechanism in the scabbard that allowed wisteria flower poison to flow with each thrust. While the demon clashed with Giyuu, she slid in from the flank. A thrust. Aimed at the neck. It pierced. Poison flowed. But——the demon did not flinch. The wound sealed immediately. The regeneration speed did not decrease. (It's not working. It's breaking down the poison inside its body.) Judgment descended in Shinobu's mind. Standard concentration was insufficient. This demon had power near the Upper Moons. Giyuu parried the demon's attacks while gradually being pushed back. The demon's Blood Demon Art continued to lower the surrounding temperature. The ground froze, worsening the footing. Giyuu's movements became slightly duller. In that moment. The demon raised one arm. The air split. An ice blade——a sharp chunk of ice created by Blood Demon Art flew toward Giyuu. Giyuu turned his body instinctively. He turned toward Shinobu. He became a shield. Slash. The ice blade pierced Giyuu's right shoulder. Blood sprayed. "Tomioka-san!" Giyuu's expression didn't change. He switched his grip on the blade and charged at the demon again. The movement of his right arm was clearly dulled. Yet he did not stop. Shinobu gritted her teeth. (Stay calm. Do what you can now.) She pulled a bottle from the leather pouch. The experimental poison—threefold concentration, still unstable. She hadn't confirmed its safety yet. But this was all she had now. The demon laughed even as it received Giyuu's attacks. It continued to regenerate. Shinobu moved. Giyuu drew the demon's attention from the front while she circled to the flank. She applied the experimental poison to her blade. One breath. Total Concentration. She released a thrust. The moment it pierced the demon's neck, poison flowed in. ——The demon's movement stopped. Regeneration visibly slowed. The wound would not seal. "Now!" Giyuu was already in position. Water Breathing, Eleventh Form——Calm. A form Giyuu had created himself. Like a water surface without a single ripple, it negated all techniques while delivering a single strike. The demon's head fell. A moment of silence in the night air. Then the demon's body began to crumble like sand. Dissolving. Just before it vanished——the corner of its collapsing mouth curved slightly upward. "Heh……interesting poison." A rasping voice. Then it turned to ash. Only the sound of flames remained. Shinobu rushed to Giyuu's side. "Sit down. Show me your shoulder." Giyuu obediently lowered himself to the base of a nearby tree. When he removed his haori, the wound on his right shoulder came into view. A deep wound where the ice blade had pierced. The wound was cold, sensation dulled. Shinobu moved with practiced efficiency. She pressed cloth against it, applying pressure. She continued treatment while checking the blood seeping out. "[serious]Please don't be so reckless." She said this while her hands never stopped moving. Giyuu paused for a moment. His gaze fell to the back of Shinobu's hand. Skin roughened from handling poison. Stains on her fingertips. Evidence of continuous experiments yesterday and today. "You too." He said only that, curtly. Shinobu was at a loss for words. She tried to say something, then stopped. She had no comeback. She finished the treatment and stood. Giyuu stood as well. The movement of his right arm was still awkward. Shinobu moved to his left side and offered her shoulder. Giyuu turned his face toward her for just a moment. He said nothing, but he did not refuse. The two left the settlement. They began walking down the mountain path. Both were battered and worn. Yet their feet moved. The way they walked——their breathing was more in sync than the night before. Night wind blew. The smell of smoke drifted from the settlement. The moon hung above the mountain ridge. As she walked, Shinobu replayed the voice in her mind. Interesting poison. That single parting word from the demon. Not mere sour grapes. It sounded like it knew something. Something about the experimental poison——had it recognized it? (And that ice-controlling Blood Demon Art……) The technique the demon had used to manipulate cold. It bothered her. There was something catching about the way it used the technique. It felt connected to the words the Lower Moon had spoken last night——something larger is moving——but she couldn't quite grasp it. The shape wouldn't form. (I can't think clearly right now.) Giyuu's weight rested on her left shoulder. Shinobu looked ahead and kept walking. She quietly tucked that unease away, deep in her chest.