"Eiji Kaito."
Someone called my name. I blinked and pulled my gaze from the window where fog clung to the glass. My mind looped back to the purple envelope from that morning, the haiku inside still nagging at me.
"Twisted guard sticks to our hands."
It felt familiar, like I'd heard it before. It tugged at something buried. I was trying to drag it up when something soft tapped my shoulder—an eraser.
Ms. Song was calling me.
I turned and caught Hani's quick grin from the seat next to mine. She'd switched spots that morning, claiming the back row had a "better view of the board." Sure. She'd been squinting at the front all morning, so that seemed unlikely. But her eyes still carried that spark from back then—something I shouldn't have been noticing this much.
Ms. Song's voice sharpened. She tapped the board, exasperation mixing with expectation on her face.
"Alright, since you're back with us, answer the problem on the board."
I glanced up.
The problem read: "Find all pairs of prime numbers (p, q) such that: p² − 2q² = 1."
Chalk dust hung in the silence. A few students leaned forward. Most didn't move—just stared, trying to find a foothold.
I didn't move either. But the structure clicked before I finished reading it.
A Pell equation. I'd seen ones like this before—they looked endless until you started adding restrictions. Primes didn't like to stay together in sequences like that. The answer was hiding somewhere small. I'd already spotted it.
Done.
Someone muttered about trial and error. Another tried plugging in small primes one at a time. Nobody had recognized the shape of it.
I had. So I stayed quiet.
Hani's sneaker bumped my foot. A little code from grade school: You good?
I tilted my head half a degree: Yeah. But I'm not saying it. Not here.
Ms. Song turned to Hani instead.
"Only one pair," Hani said, flat and fast. "(3, 2). p equals 3, q equals 2."
Silence hung for a beat. Then whispers rippled through the room. A guy up front twisted around, eyebrows raised. "How'd you get that so quick?"
Ms. Song nodded, faint approval in her eyes that made my skin itch.
"Correct, Hani. Impressive work." She paused, her gaze sliding back to me. "That's what happens when you don't daydream during class."
A few heads turned my way. Instant punchline. The spotlight I'd dodged swung right back, and my face burned under the attention I never wanted. Hani accepted Ms. Song's praise with a small smile, but the quick look she shot me flickered with understanding—she'd read my retreat perfectly.
I twisted the Rubik's cube under my desk. The clicks steadied me as the lesson dragged on. Across the aisle, two students started arguing about proofs from yesterday's quiz.
I slumped deeper into my chair, willing it to swallow me whole.
—--
The final bell cut through everything. Chairs scraped. Bags zipped.
Hani caught my arm at the door. "You dodged that Pell equation on purpose." Not accusing—amused. Dark circles sat heavy under her eyes. She wasn't sleeping enough.
I shrugged. "You had it handled."
"That's not the Eiji I knew before." She held my gaze a beat too long, then her phone buzzed. She frowned at the screen. "Ms. Song. Needs help grading quizzes."
Her shoulders sagged. "Go to the club without me. I'll catch up."
She veered toward the old building before I could answer.
—
The second floor of the library building was empty.
Fog pressed against the windows like something trying to get in. My footsteps echoed off tile that nobody had bothered to replace. The lights buzzed at a frequency that made the silence louder.
Building-D's polish was a world away. Up here, the paint was chipped, the corridors narrow, the ceiling lower. A different school buried inside the same one.
"Twisted guard sticks to our hands."
The haiku surfaced uninvited, cutting through the silence like a voice in an empty room. I shoved it down, but it clung—familiar, personal, aimed.
A shadow shifted at the far end of the corridor. Someone turning away fast. I stopped.
Nothing. Just fog against the windows and the low groan of old pipes.
I kept walking. The weird feeling didn't.
Michi was pacing in front of Room 722, her usual confidence frayed at the edges as she fidgeted with her hair tie. She spotted me and exhaled.
"Eiji, thank goodness you came. I need your help."
She stopped as I approached, eyes flicking to the door. A heavy padlock hung from the handle, gleaming under the dim lights like a taunt. It hadn't been there yesterday. I froze.
A riddle was taped to the lock, crisp paper with bold print:
Three unique primes.
First two sum to 42.
Last two differ by two.
Product is your key.
Number theory again? Just like Ms. Song's problem this morning.
"Is this a prank or a test?" I asked, keeping my voice low. My fingers found the Rubik's cube in my pocket. The clicks grounded me.
Michi shook her head, a crack in her poise. "It's not like that. The club's application form is inside. I have ten minutes to get it to the Student's Affairs Office or the Mystery Club's done. No restarts. No appeals. Someone locked it right after I left to grab signatures."
It mirrored the topic from class. The advanced curriculum was deep in number theory—who else would have made this?
Who's watching us?