The wall separating Room 201 from Room 202 was approximately 15 centimeters thick.
Based on the acoustics, it was likely composed of cheap drywall and minimal insulation. This meant that sound traveled through it with an efficiency that was annoying for a tenant, but fascinating for an observer.
It was 11:42 PM.
I lay on my futon, staring at the stained ceiling, my arms crossed behind my head. My breathing was rhythmic, controlled.
On the other side of the wall, Aoi Hoshino was crying again.
It wasn't a loud, dramatic cry. There were no screams, no throwing of objects. It was a low, muffled sound—a series of stifled gasps, like someone trying to scream underwater.
Variable A (Aoi) is releasing cortisol and adrenaline due to prolonged social stress, my brain analyzed automatically. The logical response would be sleep. Crying expends hydration and calories with zero return on investment. It is inefficient.
And yet, she continued.
I turned on my side, facing the wall. I placed my hand against the cold, painted surface.
The vibrations were faint, almost imperceptible.
Why didn't she fight back? I had run the simulations in my head during dinner. If she had flipped the desk when those girls insulted her lunch, the probability of them bullying her again would initially spike, but then drop as they realized she was a high-effort target. Bullies, like electricity, follow the path of least resistance. By being passive, she was making herself the most conductive path.
"Illogical," I whispered to the empty room.
The crying stopped abruptly.
I froze. Had she heard me? No, the wall wasn't that thin.
A moment later, I heard the sliding sound of glass. The balcony door.
She was going outside.
I checked my internal clock. If I went out now, the probability of an awkward encounter was 98%. The logical move was to stay in bed.
I sat up and grabbed a hoodie. Apparently, tonight, I was ignoring logic.
The night air was crisp, smelling of distant rain and the stale smoke of the city.
The balconies of Sunset Heights were small—just narrow strips of concrete separated by a frosted glass partition. You couldn't see your neighbor clearly, but you could see their silhouette. And you could certainly hear them.
I stepped out, leaning against the railing. I didn't look toward the partition. I looked at the streetlights flickering below.
"You're awake," a voice came from the other side of the glass.
It was hoarse, rough from crying.
"Insomnia," I lied. "The silence is too loud."
A pause. "That... sounds like something a poet would say."
"I'm not a poet. I'm a realist. Silence implies a vacuum, and nature abhors a vacuum. My brain tries to fill it with noise."
She let out a small sound. It might have been a laugh, or a cough. "You talk weirdly, Kageyama-kun."
"So I've been told."
I took a sip from a can of coffee I had brought out. I waited. In negotiations, the first person to speak usually loses leverage. I wanted to see what she would say.
"About today..." she started, her voice barely a whisper. "In the classroom."
"Forget it. It was just rice."
"No," she interrupted. There was a sudden firmness in her voice that surprised me. "Not that. I mean... thank you for not helping me."
I blinked. That was... unexpected.
"Explain," I said.
"If you had stood up for me," Aoi said, her silhouette leaning against the railing, mirroring my pose, "Subject A—I mean, Rio and her friends—they would have targeted you too. Or they would have said I was... you know... using my body to get guys to protect me. It would have made it worse."
I stared at the frosted glass.
She understood the social dynamics. She wasn't just a passive victim; she had calculated the outcome of an intervention and realized it was negative. She was enduring the bullying not because she was weak, but because she was trying to contain the damage. Minimizing the blast radius.
She is applying game theory, I realized. Suboptimal strategy, but a strategy nonetheless.
"You're smarter than you look, Hoshino," I said.
"Is that a compliment?"
"It's an observation. Most people in your situation just pray for a savior. You're managing the threat."
"I'm not managing anything," she whispered, her voice cracking again. "I'm just... trying to survive until graduation. 480 days left."
480 days. She was counting.
"That's a long time to hold your breath," I said.
"I have good lungs."
Silence fell between us again. But this time, it wasn't awkward. It was a shared understanding. The 'Unsolvable Girl' had just given me a variable I hadn't accounted for: Resilience.
"Go to sleep, Kageyama-kun," she said softly. "And... thanks for the 'you missed a spot' comment. It helped. It made me focus on cleaning instead of crying."
I heard her door slide shut.
I stood there for a minute longer, finishing my coffee.
"She thought I was being kind," I muttered, crushing the empty can in my hand. "I was just testing her reaction time."
But as I walked back into my room, I couldn't deny the data. My pulse was slightly elevated.
Problem complexity: Upgraded from 'Simple' to 'Advanced'.
The next morning, Seishin High School was buzzing with the frantic energy of impending exams.
I walked into Class 2-B, sat at my desk, and immediately engaged 'Stealth Mode'. I opened a book on Advanced Calculus, hiding it inside my English textbook.
Aoi arrived two minutes later. Her eyes were slightly puffy, but she walked with her head down, sliding into her seat like a shadow.
"Hey, did you see the new episode of that idol show?"
"Totally! The way he danced was so cute!"
The background noise of the class was consistent. Until it wasn't.
I saw movement in my peripheral vision.
Rio (the bully from yesterday) was whispering to two boys near the window. They were looking at Aoi, grinning. One of the boys—a soccer player named Kenta—was holding a bottle of water. The cap was unscrewed.
They were positioning themselves.
Projection: Kenta will walk past Aoi's desk. He will 'trip'. The water will drench her uniform.
Result: Her white shirt will become transparent. Public humiliation. Sexual harassment.
Damage Level: Critical.
This wasn't just bullying anymore. This was destruction.
I looked at Aoi. She was busy taking out her notebook, completely unaware of the vector of attack approaching from her 4 o'clock.
I felt a twinge of irritation. Inefficient situational awareness, Hoshino.
I had to act. But I couldn't be seen acting.
I scanned my desk. A mechanical pencil. An eraser. A loose floorboard near Kenta's foot path.
No. Too physical. Too risky.
I looked at Kenta. He was laughing, looking back at Rio for approval. He was distracted.
I looked at the floor. Kenta's shoelace on his left foot was untied. It was trailing by about three inches.
Probability calculation...
If I dropped my eraser now, it would roll into his path. He wouldn't step on the eraser—that's cartoon physics. But if I kicked the eraser as he stepped forward, his reflex would be to adjust his stride.
I waited.
Kenta started walking. He held the water bottle loosely, ready to spill it. He was three steps away from Aoi.
Two steps.
I casually brushed my arm against my desk. My heavy, blocky eraser fell.
Thump.
It hit the floor and rolled.
Kenta didn't see it. He took the step.
At the exact micro-second his foot lifted, I stretched my leg out under my desk—pretending to stretch a cramp—and nudged his trailing shoelace with the toe of my shoe. I didn't trip him. I just pinned the lace to the floor for 0.1 seconds.
The friction was enough.
Kenta's left foot snagged. His balance broke.
"Whoa!"
He lurched forward. But because he was already leaning to 'fake' a fall onto Aoi, the momentum betrayed him. He spun wildly to avoid hitting the desk face-first.
The water bottle flew out of his hand.
It sailed through the air in a perfect parabolic arc...
...and exploded all over Rio, who was standing right behind him, waiting to laugh.
Splash.
The classroom went silent.
Rio stood there, soaked from head to toe. Her carefully styled hair was plastered to her skull. Her makeup began to run instantly.
"K-Kenta!" she shrieked, her voice reaching a frequency that hurt my ears. "You idiot! What did you do?!"
"I—I didn't—I tripped!" Kenta stammered, looking terrified. "Something grabbed my foot!"
"You clumsy moron!"
The class erupted into laughter. Not at Aoi. At Rio.
I slowly pulled my leg back, picked up my eraser, and returned to my calculus problem.
I glanced at Aoi.
She was sitting perfectly still, her eyes wide. She looked at Rio, then at Kenta, and then... slowly... she turned her head.
She looked at me.
I didn't react. I didn't smile. I turned the page of my book.
Equation balanced, I thought. The predator has become the prey.
But deep down, I knew this wasn't the end. This was just the opening move. And Aoi Hoshino was looking at me not with gratitude this time, but with suspicion.
She was realizing that the 'Quiet Neighbor' might be the most dangerous person in the room.
[End of Chapter 2]