Yamabiko stepped into the Infinity Castle and was immediately stunned by the sight before her.
The space seemed to defy gravity, and the staircases extending down from the ceiling gave it a dreamlike, almost magical quality.
Was this entire space constructed by a Blood Demon Art?
As Yamabiko wondered this, she spotted a woman in the distance holding a biwa.
Was that her Blood Demon Art?
Just as she was thinking this, the sound of the biwa echoed through the air, and a young woman in a kimono appeared not far from her.
Yamabiko stared at the unfamiliar woman in surprise, then noticed the look of disgust and contempt the woman shot her.
"Lower your head, kneel on the ground, and bow to me!"
But when the woman opened her mouth, Muzan's voice came out, terrifying Yamabiko into immediately dropping to her knees. Trembling, she offered a respectful apology: "A thousand... a thousand pardons. Your scent and appearance are completely different than before, so I..."
Muzan, however, was not satisfied with Yamabiko's explanation. He cut her off directly and questioned her coldly.
"Did I permit you to speak? Do not evaluate things through your vulgar perspective. Just answer my questions."
"..."
Hearing this, Yamabiko immediately shut her mouth. Cold sweat instantly broke out on her skin. She lowered her head even further, as if trying to burrow into the ground.
Muzan, in the form of a woman, looked down at Yamabiko kneeling and bowing not far before him. His voice carried a note of anger as he asked,
"Now I will ask you. Why are you the only one who came?"
Yamabiko kept her head down, her white hair slightly disheveled from trembling with fear. She answered Muzan in a shaky voice.
"Be... because all the others were killed. They were all killed by Sukuna!"
Upon hearing this, the expression on Muzan's face grew even uglier. Blood vessels and veins became more prominent. He pressed coldly.
"Sukuna...?"
Yamabiko hurried to explain. "He is the monster with the four eyes you instructed us to find. He calls himself Ryomen Sukuna."
Ryomen Sukuna...
Muzan repeated the name to himself, remembering he had heard it somewhere before. He decided to look into it later. For now, he continued questioning.
"So why are you the only one who came back alive to stand before me? What about Akaza?"
Because of the distance, Muzan could only confirm that Akaza was still alive, not any more precise information.
"Because Sukuna... hoped I would return to deliver a message to you, my lord..." Yamabiko said carefully.
"..."
Muzan looked at Yamabiko. He did not fully believe her one-sided story. Reaching into her thoughts, he said,
"So it was your habit of fleeing in panic whenever you encounter a Hashira of the Demon Slayer Corps that made you the farthest target from him, and thus the one chosen to deliver the message."
Yamabiko immediately stiffened. The thoughts she had buried deep inside had been seen through by Muzan without fail.
It was exactly as Muzan had said. After Yamabiko had gathered with the other Lower Moons, she had sensed the intense battle in the distance, along with the presence of Upper Moon Three, Akaza.
Unlike the other demons, who assumed Akaza had the battle won and rushed madly toward the battlefield, hoping to claim a share of the spoils to earn more of Muzan's blood and power, Yamabiko's deep-seated cowardice made her think differently. If the opponent was so easy to defeat, why would Akaza, an Upper Moon Three, be unleashing such immense power? So she deliberately slowed her pace, staying behind the other demons at a safe distance, ensuring she could retreat unharmed if something went wrong.
What happened next was still seared into Yamabiko's memory to this day.
That terrifying sight of Sukuna holding a Nichirin blade, muttering "First Form: Shiranui," and drawing a long, straight line of fire beneath the night sky that decapitated the remaining demons in a single stroke.
Yamabiko wanted to offer more excuses, but knowing she was facing this lord, any further explanation would only seem hollow. She quickly changed tack and continued divulging information.
"Su... Sukuna said he will take Upper Moon Three, Lord Akaza, to the Demon Slayer Corps' stronghold. He will wait for you there...!"
Of course, Sukuna's original words were that he no longer wanted to waste time playing hide-and-seek with Muzan. But even if she had ten times the nerve, Yamabiko would never dare say that directly to Muzan's face. So this was the polished, refined version she offered.
As Yamabiko looked up and spoke with agitation, she saw Muzan staring at her with the cold eyes of someone looking at a corpse.
"So that is your excuse for running away?"
"No, I didn't! I only came to bring you this information as quickly as possible..." Yamabiko explained excitedly, tears of fear streaming from the corners of her eyes.
Before Yamabiko could finish her explanation, an inhuman, sinister mass of flesh erupted from Muzan's right sleeve and devoured her instantly. Blood splattered across the floor of the Infinity Castle.
Muzan had killed her so cleanly and decisively because he had concluded that things like Lower Moons had no value in existing. They could not even handle the Hashira of the Demon Slayer Corps. And now, when faced with that man, they had simply run away. They were utterly useless, the worst of the worst.
It had to be said that Muzan was intrigued. If Sukuna truly did as he said and exposed the location of those Demon Slayer Corps rats' stronghold, it would save Muzan a considerable amount of time. He could also eliminate Sukuna at the same time, eradicating both forces currently obstructing him in this world completely.
Worried about an ambush? Muzan was not like those worthless Lower Moons. He had never considered those people a threat. Nor did he believe that the Upper Moons remaining to him would lose to those swordsmen.
Even if not for Sukuna or the Demon Slayer Corps, Muzan needed to confirm Akaza's current situation. Had he been defeated, or... betrayed?
Although the curse within Akaza's blood had not activated, the fact that Sukuna had not killed him was an extremely abnormal act. Combined with Sukuna's mysterious powers and the interrogations of the other demons, Muzan was not entirely certain whether Sukuna possessed a means to make Akaza betray him without triggering the blood curse.
Just then, the sound of the biwa rang out. Upper Moon Five, Gyokko, and Upper Moon Four, Hantengu, appeared at the spot stained red with Yamabiko's blood.
Muzan spoke coldly. "You both heard that, yes? Find that man's location. And find Akaza."