Chapter 32: “The Trap of the Underwater Observation Window (The Three Being Observed and the Logic of Reversal)”
“...Pa‚ it went *crack*. Just now‚ my ‘maiden’s sixth sense’ didn’t miss that nasty sound‚ like biting into a bag of potato chips past their expiration date…!”
I shook my hair that had just been softly repaired with baking soda and pointed at the huge circular window spread out beneath our feet on the observation floor.
Just a moment ago I’d been gazing dreamily at the sunset that looked like a strawberry on top of a parfait floating in the sky‚ but the “vertical sanctuary” beneath our feet suddenly began to play an ominous melody.
“...Nagisa-san‚ quiet. ...The sound source is the reinforced acrylic on the floor surface‚ thirty-two centimeters from the joint.”
Haru-kun crawled onto the floor while protecting his broken right leg.
He opened the waterproof notebook we had bound just yesterday‚ still carrying the scent of wax‚ pressed his thumb to his lips‚ and began staring intently into the depths beyond the window.
“...Strange. The thickness of this window is eighty millimeters. The current external water pressure is estimated at 1.5 atmospheres. The design safety factor should maintain 4.5 times that. ...And yet the way this crack runs is not physically beautiful.”
Haru-kun quickly scribbled formulas in the notebook.
For him‚ the world must look different from the scenery we see—probably a place like a matrix where countless numbers fall from the sky.
“Not beautiful… Haru-kun‚ this isn’t the time to give a fashion check to a crack! Look‚ those lightning-like lines are getting more and more ‘refills’!”
“Nagisa‚ don’t move. ...The load will fluctuate.”
A low‚ heated voice echoed from behind.
When I turned around‚ Rin-chan—our “main engine”—was standing there‚ her white shoulders visible beneath her sleeveless jacket. Red rope marks from when she hoisted us up like weights remained proudly on both shoulders like medals of honor.
Rin-chan knelt beside me and leaned her face close enough that the heat from her bare shoulder brushed my arm.
“...Haru is right. If it were a uniformly distributed load from water pressure‚ the cracks would spread radially. But this—too much ‘stress’ is concentrated in one spot. As if something from the outside is targeting us precisely… selecting us and striking—”
“Selecting? ...Hey‚ Rin-chan. My ‘people-in-trouble sensor’ has been receiving some weird ‘stares’ for a while now.”
I gently placed my right hand on the cold glass.
My plastic-bottle shoe on my right foot made a *mugyu* sound‚ and the tourniquet (AC adapter) shot pain straight through my skull. But thanks to that pain‚ my intuition was sharpened.
“Beyond the window… in the dark sea‚ I feel like someone is staring at us‚ like a naughty kid aiming for the last bite of a parfait.”
“...A gaze‚ huh. Unscientific‚ but it matches Haru’s calculations.”
Rin-chan lifted the corner of her mouth fearlessly. In her eyes shone the cold‚ sharp light unique to a fixer determined to find the bugs in the world and crush them by force.
“If it’s an error with ‘intent’ outside‚ we’ll just rewrite it into the ‘specifications.’ ...Haru‚ write the blueprint for the next repair in that notebook. ...We’re not just fixing it. We’ll rebuild this window into a ‘trap’ to welcome them.”
Haru-kun’s pen began carving “equations of battle” onto the blank Day 2 page—different from the survival records before.
The world observing us. And our three-person “brainstorming session‚” staring back and launching a counterattack in the name of repair‚ was about to begin.
“...Hey‚ Haru-kun. That notebook’s about to turn into a ‘collection of insults about the world.’”
I peeked at Haru-kun’s back as he crawled on the floor‚ scribbling formulas with total focus.
His notebook was the ‘Day 2’ page we had firmly bound with wax yesterday. Now it was filled with the angles of cracks in the observation window and graphs of rising water levels—like tracking the footprints of an invisible enemy.
“...No‚ Nagisa-san. This is ‘verification.’”
Haru-kun stopped his pen and pointed toward the dark sea beyond the window while still in his distinctive crouched posture.
“When we repaired the radio in that abandoned office‚ we observed a 0.4% acceleration in the sinking speed. And the magnetic anomaly that disturbed the compass when you saved me in the fog. I thought those were independent errors… but when we add the stress concentration on this observation window to the calculations‚ a terrifying hypothesis emerges.”
“Terrifying…? Don’t tell me the expiration date of this world is tomorrow or something?”
“...Statistically speaking‚ this world is breaking while ‘aiming’ at us. The periodic magnetic anomalies are interfering with our approach to Momiji-san’s observation tower. And this crack in the window—this is a physical checkmate meant to deny our solution of ‘vertical evacuation.’”
Haru-kun’s voice carried the pure ring of despair that comes only when emotion has been stripped away.
“So it’s targeting us… Nagisa‚ what do you think?”
Rin-chan‚ arms folded beside me as she stared at the cracks‚ turned her gaze toward me.
I listened to the small *mugyu* sound from my plastic-bottle shoe and sharpened the spreading pain in my thigh as my own kind of “sensor.”
“My sensor hears it like this. ‘Hey‚ why not give up already? It’s about time you became sashimi‚’ like some mean god giggling. Basically‚ this world is trying to scare us into choosing to sink on our own.”
“...Choose to sink on our own?”
Rin-chan frowned. I lifted my useless left arm with my right hand and tapped the window glass.
“Exactly! The opponent is waiting for our ‘excitement index’ to hit zero! That’s why if we just fix it‚ they’ll break somewhere else.”
My intuition‚ Rin-chan’s engineering‚ and Haru-kun’s statistics.
The three separate perspectives clicked together in the dense air of the observation room.
“...I see. If the opponent is moving the board with ‘intent‚’ then we’ll trap them using the ‘rules’ called physical laws.”
Rin-chan’s smile turned fearless. She no longer looked like a repairer protecting something—she looked like a cold strategist aiming for fate’s vital point.
“Haru‚ calculate the curing speed of the sealant. Nagisa‚ with just your right hand—use the ‘mirror fragment’ you’re holding as a wedge and prepare to deliberately widen the tip of this crack.”
“Eh!? We’re trying to fix it and you want to break it more!?”
“...Ordinary repair is over. What we’re doing now is a ‘counter-trap’ using the structure.”
A narrow observation room. Shadows writhing beyond the window.
Our ‘Day 2’ accelerated into an intellectual fistfight with the world.
“...Alright‚ Haru. Calculate the curing time. Nagisa‚ stay there and act as a ‘paperweight.’”
With Rin-chan’s command‚ construction of our ‘counter-trap against the world’ began.
The stage was the huge circular underwater observation window embedded in the observation floor.
Beyond the window had already become a completely “black sea‚” and the water pressure pushing from there made the glass scream even louder.
“Roger! I’ll put this ‘asset’ of mine—my body weight—to good use!”
I hugged my useless left arm with my right hand and locked my plastic-bottle shoe—“Nagisa Hover”—firmly against the window frame.
The AC-adapter tourniquet dug into my thigh‚ pain hammering my head‚ but the pain became the best signal telling me: *I’m not broken yet.*
“...Nagisa-san‚ tilt your right foot three degrees further inward. According to my calculations‚ placing your center of gravity there will offset fifteen percent of the stress intensity factor acting on the crack tip.”
Haru-kun’s pencil raced across the waterproof notebook.
His numbers are always complicated enough to make my brain’s “excitement index” lag sometimes‚ but I know they’re the magic spell that turns this desperate situation into a solvable game.
“Three degrees inward… like this! Alright‚ I’m the world’s heaviest piece of stationery now!”
As I pressed the window down with my whole body‚ Rin-chan slid in beside me.
The narrow window space.
Her bare shoulder lightly touched my back.
“...Eep.”
Even though we’d been soaked in cold rain‚ Rin-chan’s skin was surprisingly hot.
The leftover heat of the muscles that had pulled a 140-kilogram sled flowed straight from her sleeveless shoulder to my arm.
The smell of sweat and the powdery scent of the baking soda we used as dry shampoo earlier.
Whenever Rin-chan’s body heat brushed my nose‚ the drill in my heart started spinning wildly—for reasons unrelated to survival probability.
“...Don’t move‚ Nagisa. ...I’m going to fill this crack with a mixture of baking soda and resin.”
Rin-chan didn’t seem to notice my red face as she carefully packed sealant into the crack.
But the way she applied it was strangely uneven.
“Hey‚ Rin-chan. The way you’re applying that… aren’t you intentionally leaving the edge open?”
My intuition caught the technical “discomfort” in her work.
“...You noticed. ...This isn’t a repair. It’s an intentional relocation of the structure’s ‘weak point.’”
Rin-chan’s eyes flashed as she smiled.
That fearless smile pierced my chest again.
“According to Haru’s calculations‚ this crack was caused by ‘interference’ from outside. If we just seal it‚ they’ll strike somewhere else. So we deliberately leave this one place as a ‘pressure escape route.’”
“Escape route…? Doesn’t that mean water will burst out and we’ll end up as sashimi!?”
“...The opposite. When you pinch the tip of a hose‚ the water shoots out harder. Same principle. That momentary burst will be the trigger. The instant something outside hits the window again and presses on this tiny gap—this window will return the several tons of water pressure it’s holding as a ‘water-pressure bullet’ fired from that single point. Straight into their skull.”
Rin-chan’s hot fingers overlapped mine as we pushed the sealant in.
Cold glass‚ warm skin‚ and an intellectual conspiracy called “counterattacking the world.”
Inside the sealed observation room‚ our body heat melted together‚ rewriting the time waiting for death into a “countdown to counterattack.”
“...One hundred twenty seconds until curing. ...Nagisa-san‚ Rin-san. They’re coming. The water surface vibration amplitude increased by 0.2 millimeters.”
Haru-kun’s voice tore through the frozen silence.
In the black sea beyond the window‚ several eerie “gazes” seemed to peer at us.
“...Nagisa-san‚ don’t tremble. I’ll keep ‘observing’ the probability.”
Haru-kun gently placed his hand on my shaking knee. His fingers were cold‚ but the grip on the waterproof notebook was as firm as if all the wisdom in the world were concentrated in that single point.
“...They’re here. Multiple heat sources at the twenty-meter depth layer. ...No‚ these are not ‘organisms.’ There’s no fluctuation—almost like programmed trajectories.”
Haru-kun narrowed his eyes and pointed into the darkness beyond the window.
Huge undulating shadows circled the observation window as if they possessed will.
“The periodic magnetic anomaly and the kinetic energy of those shadows… perfectly linked. Rin-san‚ these aren’t natural phenomena. They’re the defense system—this world’s bug—rejecting our attempt to go ‘up.’”
Haru-kun’s deduction sliced the frozen silence like a scalpel.
“...A defense system‚ huh. Then it’s simple.”
Rin-chan gripped the sealant tube and smiled coldly and beautifully.
The heat rising from her bare shoulder flowed into my arm‚ repainting fear into excitement.
“Nagisa. Let’s teach some manners to the ‘naughty kids’ trying to steal our parfait. ...Now—kick there!”
“Roger! My ‘Nagisa Hover’ delivers a full-power ‘No-Entry Punch’!!”
I stomped my plastic-bottle shoe down with all my strength onto the crack tip Rin-chan had deliberately left unfilled.
PAKIIIIIN!!
A sharp sound like tearing air rang through the observation room.
The instant I stomped down‚ tens of thousands of tons of external water pressure concentrated into the deliberately created “structural gap.”
“...Obey the ‘rules’ called physical law. ...Backflow—begin!!”
Rin-chan yanked out the sealant tube like a trigger.
At that moment‚ the thick glass that had been bent to its limit snapped outward with a tremendous spring force.
DOOOOOOOOOOOOM!!
It wasn’t flooding.
The “stress concentration point” Rin-chan calculated multiplied the glass’s elasticity with the kinetic energy of the shadow that had rushed in from outside‚ firing back a ‘water-pressure bullet’ with more than double the force.
“Whaaa!? A-amazing! The shadow… it’s getting blown apart like a parfait container exploding!!”
Before my eyes‚ the eerie shadows trying to break the window were smashed down to the dark sea floor by the very water pressure they tried to use.
“...Direct hit. Structural calculation complete.”
Rin-chan breathed heavily and collapsed against the window frame.
My sweat dripped onto her white shoulder.
“...Haru. ...What happened to the ground vibrations from that impact?”
“...Damping confirmed. Hostile ‘observation’ has stopped. ...Rin-san‚ Nagisa-san. We repaired this board—the world—with our own hands.”
The sound of Haru-kun marking a strong checkmark in the notebook rang like a victory fanfare.
The body heat of the three of us melted together by the narrow window.
We weren’t just surviving.
By trapping the insane rules of this world‚ we protected our own “sanctuary.”
“...Phew! Wasn’t that ‘water-pressure beam’ from my right foot insanely cool!? That was totally a finishing move‚ right‚ Rin-chan!”
Still clinging to the window frame‚ I finally exhaled deeply.
My plastic-bottle shoe was dented from the impact‚ but it looked like a proud medal. Even the pain from the tourniquet now felt like a spice saying‚ *Being alive is the best!*
“...Not a finishing move. Just an application of Pascal’s principle. ...But the target has been eliminated.”
Rin-chan stood up‚ wiping sweat from her forehead with her sleeveless shoulder.
Droplets that bounced from the window sparkled on her white skin like scattered jewels in the twilight. The drill in my heart sped up again for a completely different reason.
“...Nagisa-san‚ look at this.”
Still crouched‚ Haru-kun held up the waterproof notebook toward us.
At the end of the complicated formulas was a bold double line and words that would define the history to come.
‘Day 2: Underwater observation. We are not baggage merely selected by the world. We repaired the laws of physics and gained the intelligence to observe the world in return.’
“Wow… Haru-kun‚ that sounds so cool! You should write the name of my finishing move somewhere in the corner too—‘Nagisa Hover Revolution!’”
“...I’ll consider it. ...Nagisa-san‚ would you like to draw something in that empty space?”
Haru-kun offered me his pencil. I took it‚ startled.
Instead of the sketchbook lost in the torrent‚ we had decided to fill this new notebook with the colors of the three of us.
With my right hand alone‚ I drew a portrait of the “naughty kid” that had shattered beyond the window earlier—something like a spiky monster inside a parfait container.
“...Your depiction of a ‘threat to the world’ lacks tension.”
Rin-chan peeked over my shoulder and muttered‚ sounding exasperated but somehow gentle.
“That’s fine! Now the dark sea beyond this window feels a little less scary‚ right?”
The three of us stood side by side‚ gazing at the sunset of the sinking city beyond the cracked observation window.
The storm of magnetic anomalies continued‚ but our coordination as a single “entity” had surely begun repairing the bugs of this world one by one.
“...Hm? ...Haru-kun‚ what’s wrong? Why are you sniffing the air like that?”
When I looked over‚ Haru-kun had closed the notebook and was inhaling the air of the observation room deeply several times. His expression regained the sharpness of a statistical detective.
“...Rin-san. The calculations have started going wrong again. The oxygen depletion rate calculated from the floor volume and our respiration rate doesn’t match the measured value. ...Something is ‘stealing’ the air in this room.”
At the end of Haru-kun’s gaze—
the blades of the old manual ventilation fan on the ceiling of the observation room had begun slowly rotating *in reverse*‚ even though there was no wind.
“...Looks like our rest is postponed again.”
Rin-chan gripped her tool bag tightly.
It seemed our Day 2 would not be allowed to end yet.
End of Chapter 32
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