Haerin led us down the narrow hallway of bound periodicals and stopped at the end, in front of a tall metal cart stacked with returns.
No one else was around.
"The scan deadline is tomorrow," she said, her voice still low. "For the book that's missing."
Hanni nodded slowly. "You mean the one Mr. Hayato mentioned last week?"
"Advanced Problem-Solving in Number Theory by Professor Tanaka. 2019 edition. Red cover. Gold lettering. The rumor started that afternoon. Quiz questions would come from that book. All year level... You can guess what happened next."
I leaned against the shelf. "Reservations piled up. Everyone wanted it. Now it's gone."
She gave a small nod. "I handled every checkout myself."
Hanni frowned. "You checked the cart? Reshelving?"
"Three times. System logs too. No logged transactions."
"Why not just report it?" I asked.
Haerin met my eyes. "Filing it turns it into a record. Records don't care who's at fault." A short, controlled breath. "I want it back before tomorrow's automated scan. After that, it's official."
Hanni shifted. "So someone took it without logging."
"Maybe." Haerin glanced down briefly. "It was last borrowed by Lee Hyein. Returned two days ago. 4:17 p.m."
Hanni's eyes flicked up at the name. Just for a moment.
The same Hyein. The timing felt wrong.
"That's the last moment I'm certain of."
Silence settled between us, then she met our eyes.
"Find it before tomorrow's scan. If it stays missing, someone will make it malice."
Then she turned, footsteps light, already heading back to the desk.
---
The final bell rang, cutting through the afternoon fatigue. Outside, the gray had thickened into something heavier, thunder still grumbling far off.
We reached the old building wing hallway. Hyein's classroom door stood open, lights already off. No one was around.
We doubled back toward the humanities wing, past the yellow door of Play With Me. The neon sign was dark. I pushed the door anyway—locked. Through the narrow glass panel, the room looked abandoned: puzzle boxes stacked, lights out, no movement.
Hanni exhaled through her nose. "Not here either."
I glanced down the corridor. "We're wasting time. Whoever was next after Hyein might know something."
Hanni nodded once, decisive. "Coco Chao. ES1 senior, top Olympiad candidate. She's under a lot of eyes. Let's check the courtyard—she likes the tables near the chapel when she needs quiet."
---
The sky had dropped lower, heavy and slate-colored. The courtyard study area sat just in front of the chapel steps—four weathered wooden tables under a long overhang, shielded from the wind.
A girl occupied the farthest one, alone. Textbooks open in a careful semicircle, a tablet glowing blue against her face. Her dark hair was pulled into a low knot, sleeves rolled to the elbows.
She didn't look up as we approached, but her fingers paused over the tablet.
"Coco-senpai," Hanni said quietly. "The Tanaka book—Haerin said Hyein returned it two days ago. We thought you might know something."
Coco's gaze moved between us, steady. Her voice came out soft, almost gentle.
"I did borrow it two days ago," she said. "Just for the day. I promised to bring it back before closing, so I did. Put it straight on the cart myself."
She paused, thumb brushing the edge of her tablet case once, twice.
"I was with Hikaru that afternoon. He's prepping for the math quiz. I walked him through a few problems on the book, that's all."
Hanni tilted her head slightly. "You didn't see it after you returned it?"
Coco shook her head. "No, it was the day of Mr. Goh's mock quiz bee in our Olympiad group session, so I was rushing. When I came back the next morning to check, it was already gone."
She gave the side of her neck a quick, absent-minded scratch—a flicker of a gesture that vanished as soon as she rested her hand on the table.
"I definitely left it on top of the cart," she added, frowning as she replayed the moment. "It should've been the first thing they scanned."
Beside her open memo pad, equations sprawled in neat rows, solutions bracketed and underlined.
In the margin, a small doodle: a five-pointed star circled by tiny dots, the lines careful, deliberate.
"You think Hikaru might've noticed something?" Hanni asked.
Coco's mouth pressed into a thin line for half a second before smoothing again. "Maybe. He was sitting right there with me. But he's… focused when he studies. I don't know."
She looked past us toward the chapel doors—tall, dark wood, brass handles catching the last of the gray light.
"He's probably still inside," she added quietly. "Piano practice usually runs until five."
A slow, lingering chord echoed from the chapel doors, then footsteps followed—measured, not hurried.
A boy appeared at the edge of the overhang, sheet music folder tucked under one arm, fingers still faintly curved from the keys. He didn't hurry, but his eyes found Coco first.
"You ready?" he asked her, voice low.
Coco gave a small nod, already gathering her things.
I spoke before they could leave. "You're Hikaru, right? Just one more thing. You both were there when the book was returned?"
Hikaru stopped. His jaw tightened for half a second, then smoothed. He set the folder on the table to free his hands.
"The Tanaka book? Yeah. She put it back properly," he said, his eyes flicking briefly to Coco before settling on me. "Reserve cart. Spine out. Barcode facing forward."
He reached up, scratched the side of his neck once, then caught himself. His hand dropped and adjusted his bag strap.
"She checks those things," he added. "Always has. It's habit."
He hesitated, then added, "I even double-checked the cart after she left. It was still there when I walked out."
I tilted my head. "And no one else was around after?"
He glanced at me, then back to the keys, fingers resting where the next chord would fall. "No one. The library was closing. Haerin was already locking the desk."
A pause.
"There wasn't anyone else around," he said, like he was closing a door. "So if something went missing, it wasn't because of her."
The word slipped out naturally. Her.
Coco's head tilted, her hand going still on her bag zipper. She just watched him, her eyes searching his for a context she seemed to be missing.
HIkaru's notebook slipped halfway out of the folder—same angular handwriting on the visible page, same margin doodle catching the light, identical spacing.
Thunder rumbled, closer now.
Hikaru glanced at Coco, then back at us. "It's a library book," he said. "If it turns up tomorrow, this all stops being a problem."
He sounded practical, not defensive.
Coco zipped her bag. Hikaru waited—close enough that their shoulders almost brushed as they turned to leave.
"If that's everything…" Her voice trailed off, polite but finished.
Hanni gave a small nod. "Thanks, Coco-senpai, Hikaru-senpai."
We watched them walk toward the school gates, side by side, steps falling into quiet rhythm.
---
As we headed back toward the library, Hanni broke the silence.
"Well?" she asked. "Any idea where the book is?"
I pulled my phone out. On it, a rough sketch of the star I'd copied from Coco's memo pad.
Five points. Careful dots. No mistakes.
I thought of the one drawn on Hikaru's notebook.
Same shape, same spacing.
"No," I said, slipping the phone back. "Not yet."