Kaito followed Rei down a hidden stairwell beneath the garage. The metal steps were old and noisy, and the air got colder the deeper they went.
"How far does this go?" he asked quietly.
"Far enough that the city can't hear you anymore," Rei replied.
At the bottom, they entered a wide tunnel. Rusted train tracks ran down the middle. Strange symbols were painted on the walls—sharp and twisting, like they were drawn by someone in a dream.
"This used to be part of the Echo Line," Rei said. "An old train route that shut down a long time ago. People forgot why. And when people forget, that's when the Hidden grows stronger."
Kaito looked at the weird symbols. "What are these?"
"They're protective marks," she said. "They keep the Hollowed out… for a little while."
Suddenly, a low sound echoed through the tunnel. A thumping—slow and steady. Kaito froze.
"Is that a train?" he asked.
Rei's face went pale. "There hasn't been a train here in fifty years."
A dim light appeared in the distance. The sound grew louder—metal screeching against metal. Then the train came.
It looked old and broken. The windows were cracked, and inside, dark shapes sat completely still. Some of them turned their heads to stare as the train passed.
It didn't hit Kaito and Rei. It passed through them—cold as ice, like a ghost.
When it was gone, everything was quiet again.
"What was that?" Kaito asked, shivering.
"A memory train," Rei whispered. "It's stuck between time. It's not alive… but not fully gone either."
Kaito looked back at the empty tracks. "What happens if someone gets on it?"
Rei was quiet for a moment. "You don't come back the same. If you come back at all."