Chapter 40: Brain Enhancement Potion
"March, Rekka, I..."
Himeko's voice trailed off as her figure appeared at the entrance of the swimming pool area. She stood frozen in the doorway, her amber eyes sweeping over the chaotic scene before meeting the gazes of Rekka and March 7th.
March 7th's neck snapped toward the door with the stiffness of a rusty gear. She looked down at herself, dripping with sticky, brightly colored liquid, and her face instantly flushed a brilliant shade of crimson.
"Ah! Himeko! It is absolutely not what you think!" March 7th jumped back, her hands waving frantically in the air. "This... this is just juice! I swear, everything dripping off me right now is really just fruit juice!"
Himeko blinked, a rare look of utter bewilderment breaking her usual elegant composure. "What?"
"Huh?"
March 7th froze, her waving hands dropping to her sides. She realized a second too late that she had completely misread the situation. Himeko had not even formed a misunderstanding yet, but her panicked, hyper-defensive outburst made it look infinitely more suspicious. She had essentially just incriminated herself for a crime no one had accused her of.
"Ahem, actually, the story goes a little something like this..." Rekka stepped in, smoothly taking control of the narrative before March could dig her grave any deeper.
He gave a brief, highly sanitized rundown of the recent events.
"Oh." A knowing, amused smile bloomed across Himeko's face as she listened. "So, you used the little notebook Rekka gave you, wrote down a wish to drink some juice, and the universe decided to deliver it by dumping it entirely over your head. Is that right?"
"Yes! Yes, that is exactly what happened!" March 7th nodded so vigorously her pink hair whipped back and forth, sending stray droplets of juice flying. "I only managed to drink half a cup before the rest spilled everywhere!"
Fortunately, her swimsuit was entirely waterproof, so the sticky mess was not a permanent disaster. The only casualty was the sheer decorative gauze tied around her waist, which would need a thorough wash before the sugar set in.
"Are you coming down for a swim too, Himeko?" March 7th asked, trying to change the subject.
"Mmm... I do not particularly need a swim right now." Himeko tapped her chin thoughtfully. "But could we perhaps change the scenery to a beach? I have a sudden craving for the seaside today."
Lying on a nearby lounge chair, dressed in a vibrant two-piece swimsuit, Ai-chan raised a hand and snapped her fingers with a crisp, echoing click.
The environment shifted instantly. The tiled edges of the swimming pool dissolved into thin air, replaced by an endless expanse of fine, powdery white sand. The enclosed water expanded outward, transforming into a rolling, azure ocean that stretched to the horizon. Overhead, the simulated starry dome of the Express gave way to a brilliant, cloudless sky. A gentle sea breeze swept through the area, carrying the distinct, crisp scent of ocean salt.
"Environmental simulation fidelity currently at 99.9 percent." Ai-chan grinned, adjusting her sunglasses. "How about it? Isn't Ai-chan just amazing?"
Himeko slipped off her shoes, stepping barefoot onto the simulated beach. She was wearing a flowing, Bohemian-style sundress today, and the artificial sea breeze caught the hem, lifting it gently around her ankles. She looked entirely at peace. She wiggled her toes, and the white sand shifted with a soft, satisfying rustle, falling away without sticking to her skin.
"This sand is incredibly comfortable to walk on," Himeko murmured, looking out over the digital waves. "It almost makes you forget we are currently hurtling through space inside a train."
"Did someone mention a barbecue event today?"
Dan Heng walked into the simulation, having already changed out of his combat gear and into a set of casual, relaxed clothes.
Right behind him, Welt stepped onto the sand. He was holding a massive, vividly colored surfboard under one arm, looking thoroughly out of place.
"Sigh. I heard you all describing the swimming pool as massive, so I specifically went back to my room to dig out my surfboard," Welt said, his voice carrying a heavy weight of disappointment.
Dan Heng slowly turned his head, his expression completely deadpan. "Mr. Welt, surfing is generally not permitted in swimming pools."
"I am well aware of that, Dan Heng," Welt sighed, adjusting his grip on the board. "I am simply mourning the missed opportunity."
"Wait, so we are definitely doing a barbecue today?" March 7th asked, having just returned from a quick change into her own casual clothes, completely free of sticky fruit juice.
"Yes, a beachside barbecue today," Himeko confirmed with a nod.
March 7th's eyes lit up like supernovas. All her previous annoyance about the juice incident vanished into the sea breeze. She practically skipped over to Himeko, looking up at her with eager, sparkling eyes.
"Himeko! Let me help you grill! I am an absolute professional at assisting!"
Himeko offered her a gentle, teasing smile. "Are you entirely sure you want to help, or are you just planning to secure the best spot to steal the food before anyone else gets a bite?"
By the time the crew finally packed up the simulation and returned to their respective quarters on the Astral Express, the clock had already ticked past ten at night.
Rekka pushed open the door to his room, the soft hiss of the sliding mechanism sealing the quiet space behind him. His gaze immediately drifted to the desk. There, lying completely still, was the diary. It looked entirely unassuming, like a cheap notebook one might buy at a corner store.
"It feels like it is missing something..." Rekka muttered, tapping his fingers against the wooden desk.
Right. The aesthetic was off.
He grabbed a pen, leaned over the desk, and carefully wrote the words 'Death Note' across the black leather cover in a jagged, slightly crooked Gothic white font.
He stepped back to admire his work. Much better. Even though he knew this particular notebook currently only possessed the power to inflict minor, inconvenient strokes of bad luck, pairing that ability with this specific cover instantly maximized the mysterious, chuunibyou aura he was going for.
A deep sense of satisfaction washed over him. It was not the actual artifact, of course, but this was arguably much funnier. The sheer sense of dramatic ceremony he would feel the next time he jotted someone's name down in this little book was going to be incredible.
"Time to get a good night's sleep."
Rekka threw himself onto the bed, pulling the covers up. He closed his eyes, and the gentle hum of the Express's engines quickly lulled his consciousness into a deep, dreamless blur.
Hours passed.
In the absolute dead of night, at the exact microsecond the hour, minute, and second hands overlapped at the very top of the clock face, the familiar, rushing sensation of cosmic separation washed over his body. It arrived precisely on schedule, a silent explosion of energy rewriting his very foundation.
A new Path descended.
The next morning, the doors to the Parlor Car slid open.
Rekka rolled into the room. He was seated in a standard-issue medical wheelchair, his posture rigid, his head tilted slightly to the side in an exaggerated display of physical frailty. His head appeared noticeably larger than it had been the night before, slightly swollen around the temples. Perched on the bridge of his nose was a pair of thick, non-prescription glasses.
"Good morning, everyone," Rekka announced, his voice flat and highly analytical.
March 7th paused mid-bite of her breakfast toast. She stared at the wheelchair, then at the glasses, and finally at his slightly inflated cranium.
"...Rekka, what exactly is going on with you today?"
"Today, I am walking the Path of [Erudition]., I have successfully researched and synthesized a special potion," Rekka replied, not breaking character for a single second.
"Your [Erudition] head was definitely not this massive the last few times you switched to that Path. Did you perform some kind of illegal modification on your own body overnight?" March 7th asked, squinting suspiciously.
"This is the physical manifestation of the Brain Enhancement Potion I developed," Rekka explained calmly, pushing his glasses up his nose with a single index finger. "Its primary mechanism is to hyper-stimulate the neural pathways, allowing the brain to perform vastly more efficient calculations. The slight cranial expansion is merely a minor side effect."
"No, no, it is way more than slight. It is incredibly obvious..."
"Why would you even create a potion like that? Just to become a little smarter?" March 7th asked, walking over to inspect him.
"Of course not." Rekka leaned back into the synthetic leather of the wheelchair, crossing his hands neatly over his stomach. He looked entirely composed, like a mastermind observing lesser beings. "When computational power reaches a certain critical threshold, one can achieve an effect that borders on precognition. By calculating the trajectory of all physical matter, mapping environmental variables, and analyzing human behavioral logic, I can predict the near future."
March 7th let out a loud scoff, leaning in close and circling his wheelchair. "Predicting the future? You are just bragging now! There is absolutely no way this young lady is going to believe that doing some fast math lets you see the future. Fine then, Mr. Genius. Calculate this: what am I going to do next?"
Rekka stared at March 7th in absolute silence for exactly one second. A supremely confident, almost arrogant smile curved the corners of his lips.
"You plan to extend your left hand and pinch my right cheek to test if the swelling is real or just a trick of the light. Upon doing so, you will find the tissue to be quite firm, and you will immediately ask me if it hurts."
March 7th's left hand, which had been stealthily rising toward his face, froze dead in the air.
"You! How did you know that!" She panicked, violently throwing both hands behind her back as if the limb had betrayed her.
Determined to prove him wrong, she bent her knees and tried to jump backward to put distance between them.
That, too, was entirely within the calculation.
"You will now attempt an evasive leap, but due to a severely unstable center of gravity, you will nearly fall. Dan Heng will then step in and support your weight with his left hand."
The moment March 7th's boots reconnected with the floor, her heel slipped against the polished metal. Her arms flailed as her body tilted uncontrollably to the left. Before she could hit the ground, Dan Heng moved with practiced efficiency, his left hand shooting out to grab her arm and lock her securely in place.
"Is this actually real..." March 7th breathed, straightening up and staring at Rekka with wide, horrified eyes. "You even calculated me slipping?"
"It was an elementary deduction." Rekka adjusted his glasses once more, the lenses catching the overhead lights. "The angle of kinetic force you applied during your jump was off by exactly fifteen degrees., the Astral Express is currently executing a minor course adjustment, meaning the friction coefficient of the floor plating was mathematically insufficient to support your chosen landing posture. In my current brain, this entire sequence was nothing more than a basic, entry-level physics model."
Sitting on one of the plush sofas, Welt lowered his morning newspaper. A spark of genuine curiosity broke through his usual stoic demeanor. He folded the paper neatly, stood up, and walked over to stand in front of the wheelchair.
"Rekka, since you claim to be able to predict the near future with such flawless accuracy, tell me... what am I about to say next?"
Rekka pushed the fake glasses up the bridge of his nose again. His eyes, which looked unnervingly deep and intense due to the bizarre swelling of his temples, locked onto Welt for two agonizingly long seconds.
"Uncle Yang, your next sentence will be: 'If you can calculate even this, I will admit that you truly possess the ability to predict the future.'"
Welt opened his mouth to speak, but the exact words died in his throat. He swallowed hard, visibly recalculating his approach.
"...That was merely a lucky guess, not a calculation," Welt countered, smoothly changing his intended dialogue. "Anyone standing in my current position would likely say something along those lines to test you."
"Then, Uncle Yang, your next question will be: 'Can you calculate my true thoughts?'"
Welt's expression instantly became incredibly subtle. A muscle feathered near his jaw.
"You—"
"Your true thought at this exact moment is that you desperately want to know if I possess the ability to predict my own actions. You want to use that data to determine whether this potion is a genuine scientific breakthrough, or if I am simply playing an elaborate parlor trick." Rekka did not even give the older man a chance to finish his sentence. "Following that realization, you will briefly consider whether you should ask for a sip of the potion yourself. However, you will immediately discard the idea, paralyzed by the fear that drinking it will cause your own head to expand, thereby ruining your carefully cultivated image as the mature, steady, and dignified elder of the Astral Express."
A heavy, suffocating silence fell over the Parlor Car. Welt stared at Rekka, his mouth pressed into a thin, grim line. He did not say a single word.
"Finally," Rekka continued, his voice echoing in the quiet room, "you will decide definitively against drinking it. But, just to be safe, you will ask me to write down the chemical formula for the potion and leave it with you. Just in case."
"..." Welt looked away, staring intensely at a blank section of the wall.
"Oh, right, I almost forgot," Rekka added casually. "You will also attempt to change the subject by asking me, 'Did you calculate where Himeko is right now?'"
Operating entirely on reflex, Welt turned his head toward the entrance of the Parlor Car.
Sure enough, Himeko was standing perfectly still in the doorway, holding a cup of coffee, watching the entire exchange with a look of deep amusement.
Having completely dismantled the psychological defenses of everyone in the room, Rekka calmly placed his hands on the armrests of his wheelchair.
He pushed himself up and stood perfectly straight, stretching his legs.
Wow, a medical miracle.
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