"Who'd bother locking a dead club?" I muttered.
Michi shook her head, voice low, fidgeting with her hair tie. "The club was huge once—riddles that packed rooms, mysteries solved all over campus. But it disbanded for some reason. At this point, it's not surprising anymore to have enemies lurking, thriving on sabotage like this."
I eyed the riddle taped to the lock. A prime riddle. Did someone from the elite section do this? Not that I cared, though. I shrugged.
"Not my problem."
"Come on, Eiji. I don't think I have much time to solve this by myself. Plus, you're a member now—you've got to help!"
I didn't really agree to become a member; she just forced it on me. Or was I kidding myself? I was ready to go and let her deal with it, but my feet didn't move.
The deadline ticked in her eyes. Curiosity hooked me, reluctant and sharp—fine, I'd peek, if only to shut this feeling.
"Show me what you've got," I muttered, dropping to the floor with my notebook. If this was a setup, I'd spot it after.
Michi knelt beside me and flipped her clipboard. "I've got all primes under 42. Pairs that add to 42—four combos. Order matters because of the 'last two.' That's where I keep stalling."
I scanned her list. The constraints were tight—first two sum to 42, last two differ by two, all three unique primes. Most combos broke on the third condition. We worked through them fast, crossing off failures, and landed on seven surviving sets.
11 × 31 × 29 = 9889
31 × 11 × 13 = 4433
13 × 29 × 31 = 11687
29 × 13 × 11 = 4147
23 × 19 × 17 = 7429
37 × 5 × 3 = 555
37 × 5 × 7 = 1295
What did "the product is your key" mean? Could it be the code itself? But which one?
Michi leaned in, breath quick. "Do we pick the one that's unique among these?"
I froze, then saw it. 4433 stood alone. The rest ended in 5, 7, or 9. Then it clicked. Maybe the code was a palindrome, same forward and back. Like some of my old puzzles, neat and balanced.
Michi frowned, her voice shaky. "But 4433's only four digits. Should we pad zeroes to make six?"
I shook my head and pointed back to the note. "First line: 'Three unique primes.' The primes are the answer, not the product. It picks the set. String them together: 31, 11, 13. That's 311113."
Michi nodded, a glint in her eye. "Oh right. It's all in the primes."
It felt right, like a lock snapping open in my mind. Four minutes left. My fingers hit the keypad: 3, 1, 1, 1, 1, 3.
Beep. Click.
The padlock popped.
Michi grabbed my wrist and squeezed—hard. "We did it! We actually—"
She caught the look on my face and dropped my hand like it burned. Smoothed her blazer. "I mean. Obviously. Math."
We pushed into the room, dust motes dancing in the stale air. The dice tray from yesterday sat untouched on the table, shelves of battered mystery books looming. Michi snatched the application form from the desk.
"Thanks, Eiji. You saved it," she said, her shoulders dropping in relief as she bolted for the office. "Let's meet tomorrow—tell Hani to come too. We'll have an official meeting by then."
I shrugged, the cube steady in my hand. But this feeling—was it from solving the puzzle, or from getting pulled in deeper? Her words lingered as she vanished down the hall—she'd hinted at bigger puzzles, things the old club had unearthed that the school buried under its shiny rankings. Not my chase, but I couldn't help thinking about it.
---
The fog grew thicker in the courtyard as the sky turned red. Fewer students hung around.
I sat on a cold bench, twisting the Rubik's cube without thinking.
Hani came out the side door, bag over her shoulder. She saw me and slowed down. Her eyes widened for a second, then lit up with that old smile.
"Eiji? Still here? Don't tell me you waited for me."
I put the cube away and kept my face blank.
I told myself I stayed to think, but I knew the real reason: Hani had texted Ms. Song she'd be late. Faculty offices closed soon. Top-student duties were trapping her again.
If I admitted it, she'd tease me and win. So I said nothing.
"Michi said to meet tomorrow at the club. Tell you to come too. Official meeting."
She laughed, light and bubbly, dropping onto the bench beside me with a dramatic sigh.
"Oh, sure, that's why you're out here freezing."
Her tease came quick, laced with that energy that always pulled people in, closing the awkward gap between us.
I shrugged. "Club's her thing. Figured you'd want in."
"Want in? After that dice game yesterday, I'm hooked. But come on, Eiji—admit it. You stuck around."
She leaned in, eyes playful, voice dropping to that old conspiratorial tone from our kid days.
"Like back when we'd solve nonsense mysteries we'd heard around the neighborhood till dark. You always acted like it was no big deal, but you never left first."
The memory hit me. Her wild laugh when we'd crack the answer and find out it was total nonsense all along.
"The club is decent. Enough to make me somewhat interested. I'm curious to see how it plays out."
She tilted her head, her smile softening, quick wit giving way to something real.
"Yeah. Mysteries are exciting. And with you around... it's like those old days. Makes all this stuff feel less heavy."
Those last words—were they a slip? I caught the flicker: exhaustion tucked behind them, like she was running on fumes but wouldn't admit it.
We sat there a moment, her chatting about random stuff—like the latest cafeteria drama and that one teacher who always forgets names—something I'd missed about her.
Then it hit: the back of my neck tingled, like someone was staring.
I looked up and scanned the foggy courtyard. Near the library building path, a dark shape stood still. Blink—gone, lost in the gray.
The locked club door didn't feel like a joke anymore. Someone was watching us.
This was bigger than a prank. Something was coming.