By the next morning, the unknown message in the class group chat had already turned into a rumor.
"Hey, did you see it?"
"They said 'debt,' right? Is this some kind of prank?"
"What if it's a teacher? Like a test or something?"
Voices overlapped as students drifted into Class 2-B, half-awake and clutching convenience store bread. Desks scraped. Chairs creaked. The steady buzz of a normal school day.
Haruto slid into his seat, placing his bag down with practiced laziness. He plugged in one earphone but didn't play any music.
He wanted to hear.
Shun leaned over from the next row, whispering, "Tanaka, did you see the chat last night? That creepy message?"
"Yeah," Haruto said. "Hard to miss."
"What do you think it was? Some scammer got in?"
"Maybe. Or someone changing their number and trying to be funny."
Shun shivered. "It wasn't funny. 'Debt' and 'interest'? Sounds like a yakuza drama."
Aiko walked in with a stack of papers in her arms, expression sharper than usual. She set them down on the teacher's desk and faced the class.
"Everyone, sit down. I have something to say before homeroom starts."
Groans rolled through the room, but chairs scraped back into place. Ryuuji jogged in at the last second, breathless, and slid into his seat behind Haruto.
"What's up with her?" he muttered. "She looks like she's about to execute someone."
"Maybe she is," Haruto said lightly.
Aiko held up her phone. "About the message in the group chat last night, the one about borrowing money with interest. I don't know who sent it, but it's not funny. The class fund is serious. We agreed to pay equally. If you're struggling, talk to me or the teacher directly. Don't turn this into a joke."
Murmurs followed. A few people looked away awkwardly. A few looked relieved.
Ryuuji raised his hand. "Did you find out whose number it is?"
Aiko's jaw tightened. "I tried calling it. It went straight to voicemail. The profile is blank. I've asked the teacher to check if someone changed their registered number without telling us."
Haruto watched her carefully. There was a fine crack in her voice—frustration, not fear. She still thought she could control the situation.
He wondered how long that would last.
Aiko continued, "Anyway, about the class fund. I'll collect the payments today and tomorrow during lunch. Please bring exactly 3000 yen. Don't make this harder than it needs to be."
Shun whispered, "Harder than it needs to be, she says, like money grows on trees."
Haruto glanced at him. Shun's uniform was a little worn at the cuffs. His pencil case had been taped back together.
It was easy to pick out who 3000 yen hurt more than others. Easy, and interesting.
Homeroom passed in a blur of announcements. The teacher mentioned the festival, exam schedule, and a reminder not to stay out too late during cherry blossom season. Standard warnings. Nothing about debt.
When the bell rang and first period began, Haruto took notes, answered when called, and laughed at the right moments. By all appearances, he was just another background student.
Only once did he let his eyes drift toward the window, to the courtyard below.
Someone had taped a small, white envelope to the bulletin board near the shoe lockers. From this distance, he could barely make it out. No one seemed to notice yet.
He smiled to himself and returned to copying the equation on the board.
By lunchtime, the classroom was filled with the rustle of bento boxes and the smell of curry bread. Aiko sat at the front, a cash box open on the teacher's desk, marking down payments on her clipboard.
"Next?" she called.
One by one, students lined up to hand over their 3000 yen. The line moved slowly, with forced jokes to ease the sting of parting with money.
Ryuuji groaned as he joined the queue. "Feels like paying tax."
"You're paying for your youth memories," Haruto said. "Isn't that worth it?"
"Memories should be free."
Haruto stayed seated, eating his convenience store sandwich. He'd already paid earlier, quietly, while most of the class was still at their lockers.
From the back of the room, he watched.
Shun reached the front, scratching his neck. "Uh… Nakamura, can I… pay tomorrow? I forgot my wallet."
Aiko's expression didn't change. "Tomorrow is fine. Just don't be late."
"Thanks, you're a lifesaver."
She wrote his name in a different color pen. Haruto noticed that, too.
Some didn't hesitate at all—kids from wealthier families, casually handing over crisp bills. Some counted the money twice before letting go. A few laughed it off too loudly.
After the line ended, Aiko counted the stack again, lips moving silently.
"How much are we missing?" Haruto asked, standing near her desk.
Aiko glanced at the list. "Four people haven't paid yet. It's still the first day, so it's fine."
"That's good."
"Isn't it?" she said, almost to herself.
She caught him looking and straightened up. "If you see anyone skipping, remind them. We don't need last-minute chaos again."
"I'll try," Haruto said.
He meant something slightly different, but she didn't hear it.
After school, the air had a different weight. The hallway felt thinner, as if someone had quietly removed some invisible support.
Haruto walked to the shoe lockers with Ryuuji, listening as his friend complained about extra practice and the coach's obsession with sprints.
"So then, he says, 'If you can still talk, you're not tired enough!' Like, what does that even—huh?"
Ryuuji stopped mid-sentence. A small crowd had gathered around the bulletin board beside the lockers.
"What's going on?" he asked, craning his neck.
Haruto already knew what they were looking at.
A white envelope was pinned to the board with a single thumbtack. On the front, in neat handwriting:
To: Class 2-B
From: The Exchange Committee
Someone had slid a paper halfway out of the envelope so that the first line was visible.
Ryuuji whistled. "Exchange committee? What club is that?"
"It's not a real one," someone said. "I checked the club list. There's nothing like that."
"Maybe it's about the cultural festival…"
Aiko pushed her way through the cluster, frowning. "Move. You can't block the lockers."
The students parted reluctantly, making room for her. She pulled the paper fully out of the envelope and scanned it.
Her expression changed. Just a little. Her lips pressed tighter.
"What is it?" Ryuuji asked. "Some weird flyer?"
Aiko didn't answer right away. She read it again, as if hoping the words would change.
Haruto watched, silent.
Finally, she spoke. "It's for us. Class 2-B."
She cleared her throat and read aloud.
"'Dear Class 2-B of Seiran High School. We have observed that your class has recently raised a fund of 90,000 yen for the upcoming cultural festival. That's a lot of money to trust your classmates with, isn't it?'"
Uneasy chuckles scattered around.
"'We would like to offer you an exciting opportunity: a chance to multiply your funds… or lose them entirely.'"
The hallway went very quiet.
Aiko's voice tightened. "'If you choose to participate in our little exchange game, please send one representative from your class to the old audio-visual room on the third floor, today, after school, before 5 p.m. If no one comes, we will assume your class prefers safety over profit.'"
She reached the end. "'However, if you're curious… be prepared to accept the consequences. Sincerely, The Exchange Committee.'"
Someone laughed weakly. "What is this, some kind of festival stunt?"
"Must be a prank," another said. "There's no way it's real."
Shun whispered, "Multiply our funds, huh…"
Ryuuji snorted. "It's obviously fake. 'Exchange Committee'? Give me a break. Probably some bored third years."
Aiko folded the paper sharply. "Whoever's doing this, it's not funny. I'll show this to the teacher."
She turned as if to march straight to the staff room.
"Wait," Haruto said.
The word slipped out before anyone else could move. A few heads turned toward him, surprised.
Aiko paused. "What is it, Tanaka?"
He looked at the paper in her hand with mild curiosity. "If it's a prank, confronting the teacher won't change much, will it?"
"It will at least stop whoever's behind it from bothering us."
"Will it?" he asked. "They didn't ask for money directly. They asked for someone to come to a room. It's more like… an invitation."
"Exactly," Aiko said. "And we don't accept invitations from strangers, especially ones talking about money."
Ryuuji crossed his arms. "Haruto, you're not seriously thinking of going, right? You hate trouble."
Haruto smiled faintly. "Just curious. If we ignore it and they're serious, what then?"
"What do you mean 'serious'?" Shun asked nervously.
"Say there really is someone running a 'game' with money involved," Haruto said casually. "If we don't go, maybe nothing happens. Or maybe they decide we're boring and target a different class. But if they went this far just to get our attention…"
He let the sentence trail off.
Aiko's eyes narrowed. "You're overthinking it."
"Probably," Haruto agreed. "Still, wouldn't it be safer to send someone just to check? If it's a prank, they can report back and we all laugh about it. If it's not…"
He shrugged. "We'll know what we're dealing with."
The group shifted uncomfortably. The idea of "not knowing" bothered them more than they wanted to admit.
Ryuuji scratched his cheek. "So you're saying we should send a scout? Like a sacrifice in a horror movie?"
"Not a sacrifice," Haruto said. "Just someone cautious."
Aiko looked from him to the others. Her sense of responsibility warred with something else—curiosity, maybe, or the fear of being left out of important information.
"If we go without telling a teacher and it turns into something dangerous, we're responsible," she said.
"If we tell a teacher, they'll probably shut it down," Ryuuji muttered. "And if it was actually a chance to get more money for the festival, they'll just say no."
"More money isn't everything," Aiko snapped.
"For you, maybe. Some of us are paying for costumes out of our part-time jobs," a girl in the back said quietly.
The hallway shifted again. Lines were starting to appear, faint but visible.
Haruto tilted his head. "We still have time before five. You can show it to the teacher first, Nakamura-san. If they tell us to ignore it, then that's that."
"And if they don't?" she asked.
He smiled. "Then we choose someone very careful to go. Someone who won't get swept up easily."
Ryuuji jabbed a thumb at him. "Then you go. You're the most boring guy I know. Not even a cult could recruit you."
A few people laughed, tension breaking a little.
Haruto raised his hands in mock surrender. "Vote of confidence, I guess."
Aiko hesitated. "I'm taking this to the teacher first. No one should go anywhere until we know what they say. Understood?"
No one argued. Not out loud.
She strode off, envelope and letter in hand.
As the group began to dissipate, Ryuuji nudged Haruto. "So, what do you really think? Is it a prank?"
"Maybe," Haruto said. "But whoever wrote that knows about our class fund. That's not public information yet."
Ryuuji blinked. "Huh… you're right. That's creepy."
He shuddered dramatically. "If some pervert in a mask shows up and says 'Welcome to the Exchange Game,' I'm running."
"Please do," Haruto said, chuckling. "I'd rather not drag you by your collar."
They separated at the exit, Ryuuji heading toward the field, Haruto toward the school gate.
He didn't go home.
At 4:45 p.m., the third floor of the old wing was almost deserted. The air was stale, the fluorescent lights flickering with a low hum. Dust floated in the shafts of fading sunlight.
Haruto stood in front of the audio-visual room, hand on the doorknob.
The teacher had made an announcement after lunch:
"Some students have received a strange invitation about money. It is most likely a prank. Do not respond. Go straight home after club activities."
That should have been the end of it.
But the envelope had been put back on the board after the teacher removed it. Someone had pinned a new message beside it:
If you're afraid, don't come.
The Exchange Game is only for those willing to risk what they have.
No one admitted to putting it there.
Haruto turned the knob and slid the door open.
The room was dim, curtains drawn. Old projectors and metal shelves lined the walls. The faint smell of plastic and dust filled the air.
"Hello?" he said.
The lights flipped on with a harsh click.
A monitor on the front desk blinked to life, white letters appearing on a black background.
WELCOME, REPRESENTATIVE OF CLASS 2-B.
Haruto's reflection stared back at him in the dark screen, small and unremarkable.
He stepped in and closed the door behind him.
"Looks like you're serious," he murmured.
The text changed.
WE ARE GLAD YOU CHOSE CURIOSITY OVER FEAR.
A small device on the desk buzzed. A slot opened, and a single envelope slid out.
Haruto picked it up. On the front:
Initial Conditions – Class 2-B
He opened it.
Inside was a short letter and something that looked very much like a list of names.
His classmates' names.
Next to each one, there was an empty space.
For a number.