I let go of my temple, and the floating eyeball vanished.
I pressed a hand to my forehead. Pain throbbed sharply, and the heart in this body was beating wildly, like it was trying to warn me.
"Tsk… it's starting again." I grimaced and dug into my haori for some medicine.
After taking it, the pain eased slowly. I exhaled with relief. This had been with me for a long time. I wasn't sure if it was a disease, or something else… maybe a curse.
I sifted through the memories in my mind. There was nothing in any scrolls, records, or stories about Muzan having an illness or curse. No records of lingering effects from facing Yoriichi Tsugikuni's Sun Breathing or the Red Blade.
This pain… it seemed to have started after I traveled through time. At first, it was mild, but now it had grown sharp and severe.
I shook my head. It didn't matter. There were medicines to ease it, and someday I could find one to cure it completely.
Once I vanished, panic swept through the others. But there was nothing they could do. I was gone, and that was that.
After that, things played out like the stories. Nezuko was acknowledged as part of the human side and became a proper demon hunter under the Demon Slayer Corps.
Tanjiro, Inosuke, Zenitsu, and the others stayed at the Butterfly Mansion for recovery. They weren't hurt physically, but their minds were drained, and they needed rest—and training.
Since becoming the Demon King, Yoriichi Tsugikuni often seemed distant, lost in thought. Even when he appeared normal, there was always something missing in his eyes.
During that time, Yoriichi would visit the Butterfly Mansion to teach Tanjiro and the others how to strengthen their bodies. The breathing methods were the same as in the stories: from the small gourd to the large gourd, maintaining total focus at all times.
Time passed. Tanjiro and the others became strong enough to carry out missions on their own. Even as a Pillar, Yoriichi couldn't always accompany them—he had his own duties to fulfill.
One day, Kyojuro Rengoku received a mission on the Infinity Train. The Crow reported that many civilians would be aboard that night, and it would be dangerous for Kyojuro to handle alone.
So the mission was assigned to Tanjiro, Inosuke, Zenitsu… and Yoriichi Tsugikuni. Yoriichi had already exceeded his mission quota for the month, so he was technically on leave. But when he learned of the danger, he asked permission to join.
Night fell.
The train was noisy, full of passengers. A distinctive figure appeared. Now wearing Western-style clothes, he stood out in a sharp suit.
Ignoring curious glances, I closed the book I'd been reading, boarded the train, and settled in a sparsely occupied seat. Legs crossed, I continued reading.
Damn, I couldn't resist coming along.
Originally, I just wanted to scout using my eyes, not take the train—but I realized I hadn't experienced this particular route yet.
Time passed slowly. More passengers came aboard. Then I spotted a familiar figure: long yellow hair, golden-red eyes, and bold eyebrows, dressed in the Demon Slayer uniform and flame-patterned haori.
Rengoku Kyojuro.
He walked straight past me. He paused briefly but didn't notice me at all. I had hidden my ghost scent, my face, even altered the smell of my clothes. Even Tanjiro might not have detected me. Kyojuro certainly couldn't—unless he could see through the world itself.
Yoriichi won't be here, right? It can't be another coincidence… I reminded myself, though a small part of me tensed.
Rengoku didn't rush to sit. He scanned the car carefully, memorizing faces.
"Rengoku!"
Tanjiro's voice rang out. I turned to see him waving at Kyojuro through a window.
Kyojuro noticed him despite his hearing issues and tapped on the glass in response. The window was directly behind me. My heart raced, but I stayed calm, watching Tanjiro from the corner of my eye.
Inosuke appeared next, then Zenitsu.
Just as I thought everyone had passed, a figure appeared that made me freeze.
Yoriichi Tsugikuni!! Why are you still following me?!
His eyes were colder than I remembered, sharper, as if he had lost something precious.
Outside, Yoriichi looked at the train with awe. Horses and carriages filled his memory—this was his first sight of such a massive machine.
"Feels… oddly safe?" he muttered, frowning as he studied it.
Tanjiro and the others boarded, moving quickly toward Kyojuro.
Tanjiro passed me first, pausing to sniff the air. His brow furrowed, but he kept walking. Hidden successfully.
Inosuke followed. He shook his pig mask, looking left and right, but continued past me. Success.
Zenitsu was next. At first, he walked without pause, then stopped to listen closely.
"There are so many heartbeats here…" he muttered.
After a moment, he left. Success.
Only one left. I lowered my head, covered my face with the book, and held my breath.
A minute passed. No movement. Have they noticed me? I peeked cautiously.
Then I met a pair of calm, piercing red eyes. They ignored everything else, fixed entirely on me.
"Mo Yunchuan, why are you running?"
!! How did he know? Is it really that easy to get caught?
I forced a casual expression and asked, feigning confusion:
"Huh? Sir, are you… asking me?"
He sat directly across from me, unblinking.
"Don't lie. You're the only one I can't fool," Yoriichi said steadily.
I looked into those eyes. It was as if he could see through everything—through my disguise, my tricks, even my heartbeat. My chest tightened, caught completely.
Wait… heartbeat? How many hearts do I even have? …Could it be?
The three strange things of the Demon Slayer world were here: the Lower Moons, the red sword, and the most confusing transparent world.
Yoriichi Tsugikuni opened a transparent world, stepping into it.
Inside it, he could see everything clearly—every breath, every heartbeat, every contraction of blood vessels, every organ, nothing hidden.
And me—the original owner of this body, Muzan Kibutsuji. I'd installed artificial hearts and brains for myself: five brains, seven hearts, scattered through my body. My appearance could change endlessly, but my true inner self… that could never be hidden.
This proved what Yoriichi had said: I couldn't fool him.
I lowered my head, closed the book covering my face, and put it on the table. My eyes glinted with frustration. I muttered through gritted teeth:
"Why can't I move freely? I'm supposed to have the final say over my own freedom."
Before Yoriichi could respond, Kyojuro Rengoku suddenly appeared. He looked at Yoriichi, then at me—blood-red eyes, cracked pupils—and his brows knit together, making his unique eyebrows squint like a wise owl.
"…Ghost."
His voice was soft, almost a whisper. Only Yoriichi, Tanjiro, and a few others could hear it, tuned in by their breathing techniques or heightened senses.
In an instant, Tanjiro, Inosuke, and Zenitsu tensed, crouched slightly, and prepared to defend.
Rengoku raised a hand, signaling them to relax. After all, Yoriichi hadn't moved. What was there to worry about?
"There are so many people here, and your row is the only empty one. Why don't we…" Rengoku said with a friendly smile, but his hand rested lightly on the hilt of his Nichirin blade, hidden at his waist.
I clenched my fists slowly, veins showing on my fair arms. I forced myself to stay calm.
"Fine. Go ahead." I said yes, but my heart wasn't in it. Damn it… I should've reserved this seat first!
At that moment, Yoriichi, sitting across from me, stood up. And to my shock… he sat down next to me.
Grass! I muttered silently.
On the roof of the train:
"Wait… six people? That's… not right."
A severed hand clung to the train's roof. Its five fingers had small mouths, each labeled with the word "dream." It was Nightmare's left hand.
The hand swiveled anxiously. Only five children had been brought here, but six humans were present now. One of them would inevitably escape the dream.
The hand paused, then the mouths twisted into a mischievous grin. A fun idea…
Back inside the carriage:
I pushed as far to the right as I could, though I hit the wall. Yoriichi was leaning toward me, taking the outer seat, forcing me into the inner one.
Why is he so close?!
Rengoku finally asked, looking at me intently:
"Excuse me… what is your purpose, ghost?"
I frowned. "Maybe get your eyes checked. Can't you see I'm on the train?"
"…Then, what's your connection to Master Yoriichi?"
Before I could answer, Yoriichi spoke for me.
"He's the ghost that escaped from the meeting. He can change his appearance at will."
Rengoku froze for a moment, staring at Yoriichi, then at me. He tilted his head, clearly trying to process it.
"Ah—! It's him—!!"
The shout startled nearby passengers, waking the three children sleeping in the seats behind.
A thin, middle-aged man in a uniform—probably a conductor—walked slowly up, holding a triangular ticket punch.
"Ticket, please."
Snap! Snap! Snap! The tickets were marked, the lights dimmed, and then… the ghost appeared.
I watched Rengoku draw his sword and slay demons. I didn't intervene. This was a show I didn't want to ruin. I was just a spectator. Once I shifted back to a familiar form, everyone relaxed, even Tanjiro.
First carriage:
Nightmare's left hand appeared, five children kneeling before him. The mouth on its back grinned and gave instructions:
"Soon, they'll all fall into deep sleep. Tie their hands while they're unconscious. Watch out—intuitive demon hunters might wake from a faint aura or ghostly smell. Don't touch their bodies!"
The children listened, expressionless, nodding like automatons.
Just as the hand was about to leave, it paused. The mouth twisted toward them.
"One of you will have to enter the dreams of two people at once and destroy their spiritual cores. Impossible, hehehe…"
Then it vanished.
Time passed quickly. Nightmare's blood demon magic began to take effect. Passengers whose tickets were marked fell into deep sleep. Yoriichi and I were unaffected… for now.
I wonder what kind of dream Nightmare will show me…
Once everyone was asleep, the five children tiptoed into the carriage. Four went first, while the last— a small girl in a green kimono—paused.
"What are you doing?! Aren't you afraid of waking them?!" she whispered angrily.
She knelt in front of Yoriichi and me—only we weren't restrained, probably because we were too close.
"Men? Hmph… strange taste," she muttered, glaring at me, then glanced at Yoriichi.
She cut a piece of rope and tied our hands together. She didn't understand why two handsome men were holding hands so tightly.
As soon as it was done, our eyelids grew heavy. She fell asleep.
Dreamland:
Yoriichi opened his eyes in the dream. Vision cleared.
In front of him was a white wall with floating photos.
Why are these photos… in color?
He looked around. Everything was familiar, yet strange—objects and walls he had never seen before.
Yet… everything here felt right to us.
It was exactly how a modern room should look.