The Weight of Synchronization
I let out a long breath.
By the time the coupling training finally ended, my entire body was drenched in sweat as if I’d just finished a brutal hand-to-hand combat session.
I’d assumed sitting in a cockpit would be easy on the body, but that couldn’t have been further from the truth.
Coupling consumed far more stamina than I expected. The concentration required to share each other’s senses and maintain that link was incredibly draining.
Thanks to that, the heat that had burned all the way to my bones from the synchronization refused to cool down. Even the cold water in the shower couldn’t completely erase the lingering warmth.
‘No wonder everyone retires so quickly.’
It was fine for now since this was just training, but once we entered real combat, things would be completely different.
The body would be pushed to its absolute limit in ways training could never replicate. After rolling around in that hell a few times, it would only take an instant for it to break down.
‘And yet Dad still sent his own daughter to a place like this. He really is something else.’
I wouldn’t go so far as to call him a mad scientist, but he was definitely not what anyone would consider a normal parent.
After all, he was the kind of person who could willingly push his own child into the role of a Dracore pilot—a job that required risking your life in battle.
Of course, being a Dracore pilot wasn’t just about being worked to death.
As I could see from the staff here, those who retired from active duty could find jobs at related institutions if they wanted, and they received generous benefits.
All those advantages had probably made the profession an acceptable choice for some people.
Even so, a sudden realization pierced straight through the center of my chest.
—I’m really undergoing Dracore pilot training right now.
Simply walking the same campus among female students inside the academy hadn’t made it feel real.
But now, after finishing the coupling training, the truth finally hit me with vivid clarity.
‘Then the real problem is actual combat, huh.’
Of course, I wouldn’t be thrown into real battles immediately. We had only just begun training, after all.
Still, every pilot eventually had to stand on the battlefield someday.
To fight the monsters known as Outers.
Even if we were smiling and training at the academy for now, I couldn’t deny that all of this was built on someone else’s blood and sweat.
When I stepped out of the shower, I spotted Yuzuki at the far end of the hallway, chatting with a few other students.
Right then, one of her friends waved and called out.
“Yuzuki, we’ll head into the classroom first!”
“Okay, I’ll be right there.”
Her friends gave light farewells and disappeared down the corridor ahead of her. Yuzuki watched their backs for a moment before turning around.
That was when I stepped forward and called her name.
“Yuzuki.”
At that instant, her shoulders jerked visibly.
She flinched and spun around with the stiff posture of someone who’d been stabbed in the back.
Then she forced the corners of her mouth upward, flashing a smile that was obviously awkward.
“...What is it?”
Her lips trembled faintly as she spoke.
The corners of her mouth were lifted, but the tension around her eyes, fingertips, and shoulders showed no sign of easing.
“Why have you been acting like this since earlier?”
“...W-what do you mean?”
“I mean… why are you so tense?”
Something had been off for a while now. Her tone and expression seemed normal enough, but that only made the nervousness she was trying to hide stand out even more.
“Who’s tense….”
Yuzuki kept forcing that awkward smile, but her cheeks had turned bright red and the end of her sentences were starting to crack.
And above all, she wouldn’t meet my eyes.
More accurately, she was pretending to look at me while actually staring at the empty space beside my head.
When I tilted my head in confusion, Yuzuki suddenly changed the subject.
“Oh, right! Oppa. You still don’t know where the next class is, do you? Follow me.”
Without waiting for a reply, she quickened her pace. It was obvious she was trying to avoid the conversation.
Her skirt fluttered from her hurried steps, and her tied hair swayed with every movement of her head.
I stared blankly at her retreating figure for a moment before eventually following after her.
As I walked behind Yuzuki, we soon arrived at the lecture hall located at the end of the corridor.
From what she’d told me on the way, today’s theory class was about the sensory synchronization system of Dracores—in other words, the mechanics of coupling.
Once inside, the room looked pretty much like a typical university lecture hall.
There was a large screen at the front, with seating arranged so students could sit comfortably behind it.
While I was wondering where to sit, Yuzuki spoke up cautiously.
“Um… I’m going to sit with my friends. What about you, oppa?”
“Then I’ll just sit nearby. It’s my first time hearing this class, so it’d be boring to sit alone.”
“...Okay.”
We ended up finding seats in the row where Yuzuki’s friends were sitting.
Instructor Kyoko had introduced me earlier, and since I’d shown my face during the coupling practice, none of them seemed uncomfortable with my presence.
In fact, one of them looked at me and joked playfully.
“Oh, the one and only male classmate has arrived.”
“Isn’t that usually called a ‘bluebird among crows’ or something?”
The others chimed in with laughter, and I gave a light bow in greeting. The atmosphere was much softer than I’d expected.
Yuzuki glanced at me as if slightly nervous, but she soon began chatting naturally with her friends.
The mood was still a bit awkward, but seeing her laugh and talk with the friends beside her made it feel a little less burdensome.
From the side, I carefully observed Yuzuki’s profile.
She was smiling brightly as she spoke with her friends.
The way she gestured with every sentence and burst into laughter at jokes was completely different from the blunt, quiet little sister I remembered.
This was a side of Yuzuki that didn’t exist in any of Yuuto’s memories—including my own.
It felt unfamiliar. Strange.
At the same time, something kept nagging at the corner of my heart.
Even now, her behavior since earlier—constantly trying to put distance between us—kept bothering me.
Not to mention the words she’d said inside the cockpit still weighed on my mind.
Hadn’t she said she was scared of coupling with me?
My thoughts kept spiraling when the front door of the lecture hall opened quietly.
The professor in charge was a middle-aged woman wearing a simple shirt and dark slacks, her hair neatly tied up. She gave off the impression of someone with strong principles.
She stepped up to the podium and began the class in a calm voice.
“Starting today, we will cover the basics of Dracore’s sensory synchronization system—also known as coupling.”
A cross-section of a Dracore’s internal structure appeared on the screen.
“A Dracore is not merely a bio-mechanical weapon. Its piloting method is a high-risk, high-precision system in which the Top and Bottom pilots share each other’s neural feedback in real time.”
She pointed at the pilot pods where the Top and Bottom sat using a laser pointer.
“This process goes beyond simply exchanging signals. It connects actual sensations—pain, tremors, body temperature, heart rate, and more. Whatever one person experiences is instantly transmitted to the other.”
The professor paused to catch her breath before adding what sounded like a conclusion.
“Therefore, the Top and Bottom must become ‘one body’ on a sensory level. The device that makes this connection possible is the ‘coupling system’ installed inside the Dracore.”
With those words, the professor’s gaze swept across the lecture hall.
And in the next moment, those cold eyes locked directly onto me.
“...I heard there’s a male student who just completed his coupling practice.”
Following the professor’s lead, every student in the room turned their attention to me. From the center of all those stares, she looked straight at me and spoke.
“Yuuto? Could you explain to the class what your experience with coupling was like?”
“Yes.”
I hadn’t expected to be called on so suddenly, but I swallowed once and answered calmly.
I decided to talk about my first coupling experience. The most recent one felt too awkward to explain to others.
“The first thing I felt was that my body didn’t feel like my own. It went beyond simply feeling connected. It was as if I was wearing someone else’s body—our senses overlapped completely.”
As I continued, the room grew quiet. A few students nodded, listening attentively.
“And those sensations… were so vivid that they were actually frightening. Body temperature, tremors, heartbeats—all of it came rushing in at once. Even though they weren’t mine, they felt completely real.”
I lifted my head and met the professor’s eyes. She was still watching me with a calm expression, but her gaze was sharp.
“What left the deepest impression, though… was the feeling that words weren’t necessary. I could sense some of my partner’s emotions. It made me feel like I understood her on a much deeper level.”
After listening to me until the end, the professor rested her hand on the lectern, tilted her head slightly, and looked at me. Her eyes held an unexpected spark of interest.
“Emotions were shared as well…?”
She stared directly at me with wide eyes and continued.
“In most standard coupling sessions, the exchange usually stops at the sensory level. The transmission of emotions… only becomes possible once a certain threshold is surpassed.”
A small ripple of surprise spread through the students. The professor silenced them with a wave of her hand and added,
“Reaching that stage during your very first coupling practice is quite exceptional. At this rate, you should be ready for real combat deployment very soon.”
I nodded instead of answering.
But inside, I was shaken.
‘…Was that unusual?’
Wasn’t that normal?
Obviously, I didn’t fully understand the exact principles behind how coupling worked.
In the original anime, those technical details had been glossed over. It was simply set up so that once their senses were connected, the protagonist and his partners could share thoughts and coordinate naturally.
Because of that, I hadn’t really grasped just how special the instructor’s comment about sharing emotions was. The characters I’d seen in the story had done it as if it were completely normal.
The professor scanned the room again before turning her gaze toward Yuzuki.
“Yuzuki.”
Yuzuki flinched slightly at her name and looked up.
“According to Yuuto’s explanation, the synchronization rate during this coupling practice appears to have reached over 80%. If there was anything significantly different from a normal coupling, could you explain it to your classmates?”
For a brief moment, Yuzuki’s pupils trembled.
“Th-that… well… that is…”
She tried to speak, but kept swallowing the ends of her sentences.
Her lips quivered, and beneath the desk, her fingers were tightly clenched.
When she drew in a breath, a tiny “Eep…” slipped out.
Her eyes widened in surprise at herself, and her face instantly flushed crimson.
The lecture hall fell into complete silence. A few students tilted their heads in confusion.
Yuzuki hung her head low, staring silently at the desk in front of her.
After a long pause, her lips finally parted very slowly.
“…At that time… it felt like everything kept overlapping. It wasn’t just my emotions—oppa’s feelings kept flooding in…”
She stopped speaking and swallowed hard.
“It wasn’t… unpleasant, but it was too… intense. It felt like even his thoughts were mixing with mine, so…”
Yuzuki couldn’t finish. She averted her gaze.
Once again, the lecture hall grew deathly quiet. The professor didn’t press further. Her eyes seemed to say that was enough.
“I see… It went deep enough that it’s difficult to put into proper words.”
The professor crossed her arms and nodded thoughtfully for a moment before continuing.
“To be honest, even during my active duty days, I never personally experienced a synchronization rate above 80%. Of course, most couplings stop at sensory feedback. The phenomenon of emotional transmission is rare, so it remains in the realm of the unknown—something that hasn’t been clearly explained even in theory.”
She flipped to the next slide. It showed a blurry silhouette of a human body with intertwined neural networks.
“During the early stages of research, various attempts were made to stabilize sensory feedback. One of those methods involved inducing sexual tension.”
She spoke calmly, as if explaining a chemical reaction, without any emotion in her voice. Yet the lecture hall stirred faintly at that moment.
The instant the words sexual tension left her mouth, most of the students pictured the same thing.
The coupling experiments that had only been conducted between female students.
And the method introduced to push past the sensory threshold.
Some swallowed hard. Others looked away. From somewhere in the front row, a strange, stifled laugh mixed with a breath escaped.
“This method is no longer used. However, there was a time when experiments involving physical contact or sexual stimulation were actually carried out under the hypothesis that coupling between lovers could induce high synchronization rates.”
At those words, Yuzuki’s shoulders twitched noticeably. It was enough to make even me, sitting beside her, feel nervous.
Although the professor’s words were quite direct, there was nothing strange about them in context.
“Of course, simply applying sexual stimulation doesn’t automatically raise both individuals’ thresholds. It requires deep focus, immersion, and emotional exchange between the two. However, because most attempts were between members of the same sex rather than the opposite sex, the results were generally poor. That is why current research focuses primarily on psychological resonance and the ‘phase coherence’ of senses.”
The professor continued explaining several more complex concepts.
Terms like phase coherence, sensory interference tolerance limits, and neural feedback loop optimization flashed rapidly across the screen.
Naturally, I understood almost none of it.
‘I should ask Yuzuki to explain this stuff to me later…’
While I stared blankly at the screen in that dazed state, the class had already ended.
The professor turned off her laser pointer and wrapped up.
“That will be all for today’s lecture. Next week, we will cover cases of coupling collapse and the associated risks. Thank you for your attention.”
Even after class ended, Yuzuki couldn’t lift her head for a long time.
I carefully turned my gaze toward her.
“…Yuzuki?”
She flinched.
She raised her head, but her eyes wouldn’t quite meet my face, as if looking somewhere else.
Then she forced the corners of her mouth up in an unnatural smile.
“Y-yeah? What is it?”
“…Class is over.”
“Ah… r-right.”
As if finally registering the situation, she silently picked up her bag.
“More importantly… let’s go eat. It’s lunchtime.”
As she carefully pushed her chair back and stood, the tips of her fingers trembled slightly.
When she slung her bag over her shoulder, her toe brushed against the desk leg and she lost her balance for a moment.
I watched her retreating figure in silence.
She walked quickly down the hallway without once looking back.
There were questions I wanted to ask, words that had risen all the way to my throat, but I swallowed them down.
In the end, I quietly followed after her.