The watching Hashira were utterly shocked when they saw Yōsuke's Breath technique and sword form.
"Kentō!"
The fastest among them, the Thunder Hashira Sayaka Raihui, tried to use Thunder Breathing to pull Kamiji Kentō, the Wind Hashira, away from Yōsuke's attack range. But before he could even get close, he was blown back and slammed to the ground by the shockwave.
At the very center of the blast zone, Kentō lay amid the ruins of a house that had collapsed into rubble from the explosion.
When the Water Hashira, Tokimoto Eriko, rushed into the wreckage to try and help him up, Kentō—who had kept his eyes tightly shut until now—suddenly opened them. His pupils gleamed with a sinister crimson light.
Picking up his fallen Nichirin Blade, Kentō slashed down—not at an enemy, but at Eriko herself.
The Flame Hashira, Rengoku Shinzuka Shō, reacted instantly, drawing his blade to block the strike as he called out:
"Kentō! What's wrong with you? Eiriko is our comrade!"
But Kentō gave no response to Shō's desperate voice. He continued to swing his Nichirin Blade wildly, attacking indiscriminately.
Shō and Eriko were forced to fight together to ward off Ken'tō's onslaught.
Meanwhile, Raihui (Thunder Hashira) and Shimazawa Daigo (Stone Hashira) had their hands poised on their blades, wary of Yōsuke.
Facing their vigilance, Yōsuke only chuckled softly and sheathed his sword.
"There's no need to be so tense. Kentō's simply been poisoned by Crimson Decay. He's just lost his reason temporarily. If you trust me, I can cure him and restore his sanity. If you don't, then just restrain him. By tomorrow, when the sun rises, the poison will burn away on its own."
At his words, both Raihui and Daigo removed their hands from their hilts. Instead, they stepped in to help Shō and Eiriko subdue Ken'tō.
Ultimately, they chose not to let Yōsuke administer the cure. Instead, they knocked Kentō unconscious, bound him tightly with ropes, and secured him to a wooden stake to wait for dawn.
Yōsuke wasn't bothered by their mistrust. After all, not everyone was like Ubuyashiki Kagaya, willing to trust him without reservation.
In their eyes, Yōsuke was not a human being, but something… other.
He paid no further mind to how they handled things. Feeling quite pleased with himself, Yōsuke left the Ubuyashiki estate and wandered leisurely into the forest.
The moment he had unleashed Blood Breathing, First Form: Crimson Decay, a system prompt had appeared before him:
"Ding. Congratulations, host, on creating a new Breathing Style—Blood Breathing. Each time the host creates a new form, you will be awarded a lottery draw."
Recognized by the system itself, this meant that Yōsuke's Blood Breathing was now officially established—a Breathing Style derived from the Breath of the Sun.
His Blood Breathing, First Form: Crimson Decay transformed his blood into crimson blossoms. As they bloomed, they burst outward in a shockwave, scattering a poisonous miasma of Crimson Decay.
For the weak—whether human or demon—the toxin corroded the body until death.
For those of Hashira-level strength, they could resist the physical corrosion, but Crimson Decay carried another effect: within the victim's heart resounded a devil's whisper, gnawing away at their sanity.
Kamiji Kentō had managed to withstand the poison's erosion of his body—but not the erosion of his reason. That was why he had lashed out indiscriminately.
However, the technique's flaw was also apparent: its casting required a long wind-up. To compensate, the crimson blossoms enveloped Yōsuke, shielding him during the process. But if faced with an opponent far stronger, they could still break through and interrupt him.
Strolling along a woodland path, Yōsuke stretched lazily. His long effort had at last borne rich fruit.
Under the moonlight, he suddenly heard the sound of a flute.
Following the melody, Yōsuke arrived at a riverbank. There sat Tsugikuni Yoriichi, playing a short bamboo flute.
Yōsuke did not disturb him. Instead, he quietly sat down at his side, basking in the rare peace.
When the tune came to an end, Yoriichi carefully tucked the flute into his sash.
"…Is Kentō alright?" he asked.
"For now, he's lost his sanity. Honestly, I thought you'd step in to stop me."
Yoriichi, still gazing at the shimmering river beneath the moonlight, spoke with calm detachment:
"I knew you would keep it within bounds. And besides—they cannot depend on me forever. They must face such trials themselves, one day."
Yōsuke's eyes drifted to the flute at Yoriichi's waist.
"That flute—was it given to you by someone important?"
Yoriichi nodded, and for the first time, Yōsuke saw him smile warmly.
"Yes. It was a gift from my elder brother."
Yōsuke immediately understood. The "brother" he spoke of was none other than Tsugikuni Michikatsu—who would one day become Kokushibō.
"What kind of person was your brother?" Yōsuke asked.
Closing his eyes, Yoriichi recalled the past.
"My brother bore a strong sense of duty and pride. He upheld propriety, and his heart was delicate. He was a formidable samurai. After joining the Demon Slayer Corps, his talent shone—he awakened the Demon Slayer Mark and even perceived the Transparent World. He became an extraordinary warrior."
"Then why was he absent from the Hashira meeting?" Yōsuke pressed.
Yoriichi's smile faded. After a pause, he answered quietly:
"Perhaps… because of me. My brother did not wish to become a Hashira. To stay away from me, he chose to hunt demons in distant places."
Sensing the sorrow in his tone, Yōsuke offered words of comfort.
"One day, he will come to understand your feelings."
"…Mm."
The two sat together by the river a while longer before returning to the Ubuyashiki estate.
The next morning, Kamiji Kentō regained his sanity. But Yōsuke was not the only one to benefit from the duel. In the crucible between life and death, Kentō himself awakened the Demon Slayer Mark. A flame-like pattern now burned upon his forehead.
With Kentō as precedent, the other Hashira followed his experience. One by one, they too successfully awakened their Marks, gaining the prerequisites for stepping into the Transparent World.
The Demon Slayer Corps had taken a great stride forward.
At the same time, Tamayo succeeded in developing a special medicine against demons. Extracted from wisteria flowers, the toxin disrupted a demon's internal structure. While it might not work on Kibutsuji Muzan, it would be devastating against his subordinates.
Everything was progressing smoothly, just as everyone had hoped.
And three months later, Ubuyashiki Kagaya formally declared:
The plan to encircle and annihilate Kibutsuji Muzan had begun.
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