The east wing of Tenryuu Academy was silent.
Not quiet — silent.
No wind. No birds. No hum of mana circuits. Just the scorched, motionless air of a place that had been too close to something it shouldn't have seen.
Ten floors down, in the infirmary's sealed wing, Reiji Sazanami sat by a hospital bed, elbows on his knees, head bowed.
The bed was empty.
Sheets still folded. Monitor still running.
But the boy who was supposed to be lying in it — Arata Kurogane — was gone.
Again.
"Third time this week," Reiji muttered. "And he still won't leave a damn note."
Yuna stood at the foot of the bed, arms folded. Her coat was torn at the hem. Her bow was missing. Her eyes looked tired — not from lack of sleep, but from too much thinking.
"This isn't a prank," she said flatly.
"No," Reiji agreed. "This is something worse."
He reached into his pocket and pulled out a folded slip of paper. It was creased and slightly burned. The edges were lined with what looked like ash.
On it, written in shaky handwriting:
> I'm awake, but it's not me.
Yuna stared at it for a long time.
She didn't ask where Reiji got it.
She didn't ask who wrote it.
Because she already knew.
---
Elsewhere in the academy, Karin Ayatsuki stood in the shadow of the old bell tower, clutching a vial of her own blood.
She wasn't supposed to be here. This part of the campus had been sealed since the Rift attack. But something was calling her.
Something beneath the floorboards.
She uncorked the vial and let a single drop hit the ground.
The blood hissed — and then spread outward in a perfect ring.
A rune flared to life. One she hadn't drawn.
A whisper echoed from below.
> "He was hollow before you lost him."
Karin's eyes widened.
And for the first time in her life, she turned and ran.
---
Meanwhile, Daigo Fushimi was dreaming.
He knew it was a dream because he was in the Hollow Realm.
Alone.
Except for the stars.
They hung low here — not in the sky, but beneath his feet, like a black ocean of constellations. Each step made them ripple.
"Hello?" he called out.
No answer.
Then he heard footsteps.
And there — standing just ahead — was Arata.
Not floating. Not monstrous. Just… Arata.
"Hey!" Daigo shouted. Relief surged in his chest. "Dude! Where the hell have you—"
Arata turned around.
And smiled.
Except it wasn't his smile.
It was stretched too wide. Lips didn't move right. Eyes too dark.
"Not him," said the Arata-thing in a voice that echoed twice.
Daigo stepped back.
"You're not—"
The thing lunged.
---
He woke up screaming.
---
Later that night, the four of them met in secret on the academy's east rooftop.
Yuna didn't speak. She just watched the horizon, where the sky still flickered from the last Rift.
Karin stood by the edge, arms folded tight.
Daigo paced back and forth, muttering to himself. His fox spirit was gone — hiding somewhere deep in the spectral plane.
Reiji leaned against the stairwell, tossing a spellcore between his hands.
"No one's saying it," he said eventually, "so I'll say it."
They turned to him.
He paused — just for a beat.
"Arata didn't survive that Rift."
"No," Karin said quietly. "Something inside him did."
Silence.
Then Yuna pulled a photo from her coat.
It was a still from a drone camera — damaged and grainy.
But unmistakable.
Arata. Standing alone. In the Hollow Realm. Smiling at the sky.
And behind him… a massive door made of bone.
---
Reiji traced the shape of the door with one finger. "That's not part of any known Rift structure."
"It's not part of our world," Yuna said.
Daigo stepped back. "We're not going after him. We can't."
No one answered.
They didn't need to.
The next morning, they left Tenryuu.
---
They crossed the southern ridgeline beneath moonlight. Broke past two barriers. Disabled three motion runes. And finally reached the edge of the Hollow Realm.
No one spoke.
No one turned back.
They descended in silence.
---
The Hollow Realm was colder than before.
Not in temperature — but in memory.
The trees whispered. The ground seemed to absorb sound. And the stars… were missing.
The deeper they walked, the more strange it became.
Reiji began hearing music in the distance — a lullaby his mother used to hum, even though she'd died ten years ago.
Yuna saw reflections in puddles that didn't match her movements.
Karin started bleeding from her fingertips — but only when she stepped too close to certain stones.
And Daigo…
Daigo saw a coffin.
Standing upright.
Waiting.
They didn't talk about it.
---
Three hours in, they found something worse than monsters.
A scout team.
Tenryuu's elite search-and-recover unit.
All dead.
No wounds. No signs of struggle.
Just... smiles carved into their faces with something impossibly sharp.
Their captain left a message on the wall, scrawled in his own blood:
> "He remembered us. That was the mistake."
Yuna dropped the note.
Karin turned away and threw up.
Reiji closed the captain's eyes.
And Daigo whispered, "It's Arata. It has to be."
"No," Reiji said. "It's what's inside him."
---
They reached the door just before dawn.
It was made of bone.
Not shaped like bone — made of it. Giant vertebrae, ribcages, and skulls fused together in impossible geometry. Some of the skulls had horns. Some had extra eyes. Some looked… human.
The door was closed.
But it was breathing.
Yuna stepped forward.
"It's not just a seal," she said. "It's a prison."
"Then what's on the other side?" Daigo asked.
Karin looked up.
And her eyes widened.
Not at the door.
At the shape standing in front of it.
A boy.
Their friend.
Arata Kurogane.
Alive.
Smiling.
But something was wrong.
He raised his hand.
Showed them the scar.
And it was gone.