The Second Partner
The path to the academy was shrouded in overcast skies, the sunlight faint and the air thick and sticky. Yet Yuzuki’s steps felt strangely light. She walked hand in hand with Yuuto, the warmth traveling from his fingertips through her skin and straight into her heart. Their body heat slowly overlapped, their footsteps falling into the same rhythm. In that moment, Yuzuki felt as if she had grown a little lighter. The confusion and caution she had clung to so tightly just days ago seemed to have quietly slipped away.
But the moment the academy’s main gate came into view, the heavy weight of reality settled over her once more. The students’ gazes. The strict rules. And the fact that they were siblings. Reluctantly, Yuzuki loosened her grip on his hand, already missing the lingering warmth. She straightened her posture as if nothing had happened. Her lips remained calm, but the emotions swirling deep in her eyes refused to fade so easily.
Just a little longer. If only we could have kept holding hands for a few more steps.
Even as that thought lingered silently beside Yuuto, Yuzuki entered the academy with her usual neat, composed stride.
As they crossed the lobby, Yuuto was suddenly called over by Instructor Kyoko. She had something to relay to him. Yuzuki paused and looked back. Their eyes met for a brief second. He gave a quiet nod. Leaving Yuuto behind with the instructor, Yuzuki continued down the hallway alone. The walk to the classroom felt a little lonely, but with her emotions now gently settled, she moved with even greater care.
Several students had already arrived and taken their seats. When the door opened, their eyes naturally turned toward her.
“Ah, it’s Yuzuki.”
“Good morning~”
The familiar voices rose in greeting. Yuzuki gave a small bow and smiled softly, just as she always did.
“Yeah. Good morning.”
A calm smile rested on her lips, yet there was a noticeably gentler aura about her today. She crossed the classroom and sat at her desk. As she quietly looked around, wondering when Yuuto would arrive, her gaze landed on the girl sitting by the window.
Luna sat in silence, staring out at the cloudy sky. She hadn’t spoken to anyone. The moment Yuzuki saw her profile, a memory suddenly flashed through her mind.
A few days ago. That complicated day when her emotions had been tangled in knots. The time she had impulsively asked Luna if Yuuto had sent her any messages. Looking back, it had been far too sudden and clumsy. Even after sending the message, she had immediately regretted it.
Yuzuki let out a quiet sigh. She no longer saw that night’s events as something so worrisome. Even if Yuuto found out, he would probably just laugh it off. It might be a little embarrassing, but that would be the end of it.
The real problem was Luna.
The fact that she had sent such a message at all kept making her feel ashamed no matter how much time passed. And more than that… Luna might already know. She might have realized how Yuzuki felt about Yuuto. No—she definitely knew.
The day they first met near the locker room, Luna had asked her directly. In that low, intrigued voice, as if she had discovered something fascinating—Do you like Yuuto?
Back then, Yuzuki had managed to deny it. Her feelings hadn’t solidified enough for the question to break her. But now? If she were asked again?
Honestly, she wasn’t confident she could deny it right away. She didn’t even want to. Because denying it would feel like denying everything she felt… as if even those emotions would become nothing but a shameful lie.
What if she spreads weird rumors to the others?
It didn’t seem like something Luna would do, but the thought still made Yuzuki glance nervously in her direction. That was when her phone, resting on the desk, vibrated softly.
The screen clearly displayed the name Sakuragi Luna.
Yuzuki instinctively sucked in a breath. Her heart skipped a beat. A tense chill ran through her fingertips. With slightly trembling hands, she opened the message.
“……”
A cold shiver ran down her spine. So she had noticed after all. Maybe she had sensed something was off. Still, Yuzuki tried to act casual and replied.
The reply came back almost instantly.
“……!”
Yuzuki’s heart sank. She reflexively glanced toward the window. From this classroom, the main gate was partially visible. If Luna had been sitting there staring outside, she would have had a perfect view.
Yuzuki pressed her lips tightly together and slowly flipped her phone screen-down on the desk. She could feel the heat spreading across her face. Even her ears were burning. Just imagining what Luna must have thought when she saw them made her head spin.
While she was still trying to sort through her tangled thoughts, the classroom door opened. A familiar presence approached.
It was Yuuto.
Yuzuki instinctively straightened her posture.
“You’re back?”
Yuuto silently set his bag down on the desk beside her and sat. Then he asked carefully.
“…Did something happen?”
Yuzuki widened her eyes and shook her head.
“Huh? No, nothing at all.”
A slightly awkward smile played on her lips, but hesitation flickered in her eyes. She quickly changed the subject.
“More importantly… what did the instructor want? She kept you for so long. Was it something important?”
“Well… I guess it was important.”
Yuuto trailed off and glanced away. It wasn’t that he wanted to hide it, but explaining felt awkward.
“She just asked if there was anyone in our class I wanted as a coupling partner.”
“…Really? She asked you that?”
“Yeah. She said if there was someone I liked, she’d prioritize them for the practical training. Something about it helping with the experimental data…”
Yuuto shrugged.
“Anyway, that was it.”
“……”
Yuzuki unconsciously let the corners of her mouth droop. She had known logically that this conversation would come eventually, but hearing it directly from Yuuto made her stomach twist painfully. They had only just started coupling. How could this topic already be coming up? It felt far too rushed, as if she was being pushed forward before she was ready.
But if she let those feelings show on her face, Yuuto would only feel uncomfortable. So Yuzuki forced her usual smile and spoke in a playful tone.
“…Hmm. So, who did you pick? It’s not Sakuragi, is it?”
After a brief pause, Yuuto answered.
“I’ll probably end up coupling with Sakuragi too if things go well this time…”
“……”
For a moment, Yuzuki’s eyes trembled sharply. Her mind went completely blank. Instead, a single raw emotion surged up from deep inside her.
I really hate this.
It came from the bottom of her heart. It wasn’t that she hated Luna. But thinking about the way she hovered around Yuuto, and how she had once sent him that swimsuit video, it was only natural for anxiety to bloom. If it was Luna, she would probably openly seduce Yuuto during coupling.
What if… Yuuto really starts to fall for her?
The thought pierced deep into her chest. Of course, even if that happened, she had already resolved to accept it. She had decided she would accept anyone. But even so, just imagining it made her heart feel unbearably tight.
At that moment, the classroom door opened and Instructor Kyoko stepped inside.
---
When Instructor Kyoko asked if there was anyone I wanted to try coupling with, I eventually answered, “Just assign me whoever you think is best.”
I still didn’t know the girls in my class well enough to single anyone out. Thanks to Yuzuki, I had exchanged greetings with a few, but those were nothing more than passing encounters. In the end, my answer was both an evasion and a delegation. It seemed more reasonable to let the instructor choose an appropriate partner.
“Hello, Nakamura-oppa.”
The girl waiting beside the training Dracore bowed her head politely. Her voice was clear, neither overly bright nor flashy, simply respectful. However, one thing caught my attention.
“…Nakamura-oppa?”
“Well, you are Yuzuki’s older brother. And you’re older than me… so I thought it would feel more natural to call you that.”
She had neat, short black hair that fell perfectly and wore her pilot suit with tidy precision. She didn’t have a particularly striking appearance, but that very ordinariness felt strangely comforting.
“Oh, by the way, do you know my name?”
“Ichihara Miyu. I know the names of my classmates.”
“That’s a relief. I would have felt a little hurt if you didn’t know mine. Anyway, please take care of me.”
Miyu gave a small smile and slowly extended her right hand. The glove of her pilot suit caught the light with a soft gleam.
“Yeah. Please take care of me too.”
I carefully took her hand. The warmth that came through the thin glove was surprisingly gentle. Even during that brief handshake, she never once looked away. The eye contact lasted a little too long, and when I tilted my head in slight confusion, she spoke softly.
“I’m sorry. This is my first time coupling with a boy… so I’m not sure what it will feel like.”
“…It’s my first time with anyone besides Yuzuki too. Honestly, I’m a bit nervous.”
“I see. Then… let’s take it slow and match each other carefully so we don’t make any mistakes.”
Her words were calm, but the gentle sincerity behind them lingered warmly in my chest.
We stood side by side in front of the Dracore. Its massive chest plating was open, exposing the cockpit. We waited briefly for the lift. When it arrived, I stepped on first, and Miyu followed quietly behind me.
The vibrating platform slowly rose. The pilot seats inside the chest gradually came into view. The interior layout was already familiar. The Top and Bottom positions were arranged front to back. Naturally, I moved toward the Top seat. The moment the suit sensors recognized the connection to the machine, the system activated automatically with a short mechanical sound.
Miyu quietly took the Bottom seat. Once both seats were locked in, the upper cockpit canopy slowly closed.
“…I’m nervous.”
Miyu gave a slightly tense smile and lay back in her seat. The sight of a girl who had only just become an adult offering her back completely felt more defenseless than I had expected. The elegant curve of her pilot suit along her spine caught the light softly. Sitting behind her, I was overcome by an indescribable sensation.
…The fact that I had to share my senses with someone other than Yuzuki. A sense of guilt, as if my emotional connection was being directed toward the wrong person. The very act of mixing senses with someone suddenly felt like undeniable infidelity.
But I had to do it.
I took a deep breath to calm my mind. The control stick automatically descended and locked precisely into Miyu’s pilot suit. With a light but firm mechanical click, Miyu’s shoulders twitched slightly.
“…Hngh.”
It was a small but clear moan. The initial coupling connection—electricity, pressure, heat, and stimulation all rushing in at once. The reaction wasn’t unfamiliar. The sequence was familiar. The response was familiar.
But the body wasn’t Yuzuki’s.
I tried not to dwell on that fact. Ignoring the rising sense of alienation, I carefully placed my hand on the control stick above hers.
Then a familiar yet strange sensation slowly began to spread through me.
It started smoothly. The faint electric current at my fingertips and the warm pressure spreading through the suit signaled the beginning of coupling.
“Hngh…”
Miyu remained composed. She occasionally let out tense breaths, but her attitude as she gradually adapted to the sensory pressure was remarkably controlled.
“Twenty-eight percent…”
Miyu steadied her breathing and quietly recited the number. I focused on my fingertips and adjusted the control stick very slowly. There was no visible movement, but the pressure must have reached her back directly—her body trembled faintly.
“Nngh… Thirty-six percent…”
A short breath escaped Miyu. I concentrated even harder. The sensation flowing from my fingertips into the control stick grew clearer. Miyu’s back muscles tensed and gave a light twitch. Along with the heat traveling through the suit, I could feel her body temperature slowly rising against my skin.
“Ah… um, Nakamura-oppa… just a moment, please…”
Miyu’s voice was trembling. The urgency mixed between her ragged breaths came through clearly. I lifted my hand from the control stick and quietly observed her reaction.
“What’s wrong?”
“Th-the synchronization rate is rising too fast… Could you let go of the control stick for a bit? I think I need to adjust…”
“Alright.”
I released the control stick as she asked. At the same time, Miyu’s breathing gradually began to stabilize. The cockpit fell silent for a moment. I waited patiently without rushing her.
After several long minutes of steady breathing, Miyu finally spoke.
“…I’m okay now. You can continue.”
I nodded and gripped the control stick again. This time I moved even more slowly, sinking deeper into the sensation. The synchronization rate, which had dropped, began climbing once more. It felt like a precise tuning as waves of sensation crossed and aligned. Even though we weren’t touching, the heat radiating from her back seemed to reach my chest. The rhythm of her pulse seeped into me through the control stick.
Gradually, Miyu’s breathing began to change. It grew shallower and more irregular than before, yet far more sensitive. The feedback spreading from my fingertips felt like electricity racing straight through the nervous system. I carefully pushed the control stick deeper.
“…Haa… Forty-four percent…”
The numbers continued to rise. A pressure that felt like it was squeezing my chest spread throughout my entire body.
“Fifty… no, sixty…? This is weird… Ngh… Why is it rising so fast… Ha…”
The air inside the cockpit grew scorching hot. Miyu’s breaths became short and broken. The tension radiating from her back pressed strongly against my palms. I didn’t answer. Unconsciously recalling the tempo I had used with Yuzuki, I added a faint rhythm to my fingertips as I adjusted the control stick.
“Nngh…! Ah, no… not that…!”
A desperate protest burst out, but it was closer to a reaction swept away by the overwhelming sensation. The tightly fitted suit. The curling back muscles. The dampened breathing. The elevated body heat from within pressed down on the entire cockpit. Her reaction was rushing toward its peak so intensely that the hand gripping the control stick began to tremble.
“Haaang…! Seriously, just a second…!”
It was the limit. In her prone position, her spine twisted violently as if in spasm. The vibration transmitted through the suit rang out powerfully.
“Ha, haa… No more…”
Finally, Miyu collapsed forward onto the control seat like a puppet whose strings had been cut. Her shoulders shook with every breath. The feedback from the control stick cut off sharply.
— Emergency Code Executed Due to Pilot Abnormality —
The interior of the craft was bathed in red warning lights.
I slowly removed my hand from the control stick. The once fiercely burning sensory feedback vanished like a lie, replaced by a subtle silence that filled the space. Below me, Miyu remained slumped over the seat, gasping for breath. Her shoulders rose and fell slowly. Thin, lingering breaths spread through the cockpit like an afterglow.
“…I see.”
It was a strangely familiar scene. Unconsciously, it reminded me of my first coupling with Yuzuki. It had been the same back then. I had unintentionally pushed the synchronization too deep, and Yuzuki had passed out from the recoil. Seeing Miyu end up in a similar state, a small wave of unease rose inside me.
Only now did I realize it—I had thrown myself into coupling without even learning how to properly suppress the synchronization rate. That truth hit me with dizzying clarity.