[2050, Classroom]
The heavy air of heat-weary exhaustion hung over the classroom.
The ceiling-mounted air cooler ran without pause, yet the air inside remained stifling and thick.
Beads of sweat formed along the backs of the students' necks, and even the surface of the desks felt faintly warm to the touch.
From the ceiling air purifier came a low mechanical hum, and the students, their arms pillowed on their desks, listened to the teacher with half-closed eyes.
"For your social studies project this term, you'll be giving group presentations."
The teacher's calm voice cut through the stillness.
"Research examples of energy self-sufficient villages and their positive and negative impacts on the community.
Then present what kind of village your team would like to create.
You'll work in pairs, and you can choose your own partners."
As soon as she finished speaking, the quiet scraping of chairs and the quick exchange of glances began to ripple through the classroom.
Jian turned her head almost absentmindedly toward the windows.
The sunlight outside had blurred into a white haze, and beyond the glass, the sun poured heat onto the classroom floor.
Near Ji-hyuk's desk, Shia was already standing there.
Holding a book, she was explaining something in a quiet but precise tone.
"Here, this part… the flow of the function formula changed a bit. You can see it in yesterday's lecture notes."
"Ah, that. I haven't reviewed it yet—thanks for letting me know."
When Ji-hyuk gave a brief smile, Shia nodded.
"It's better to catch these things quickly. Feels reassuring to have someone from the same lecture in our class."
Jian, without thinking, set down the pencil she'd been holding.
The exchange between the two felt familiar somehow.
And in the ease on Shia's face, there was a comfortable closeness— one that stirred a quiet, unplaceable feeling somewhere deep in Jian's chest.
'I didn't even know they were taking the same online class… Since when were they that close?'
All she'd meant to do was ask about working together on the assignment.
But now, for some reason, even saying a single word felt strangely cautious.
Just then, Shia turned to her.
"Jian, let's be partners for this one. Remember what we talked about yesterday?"
Jian hesitated for a brief moment, then forced a smile and nodded.
"Yeah. Sure, let's do it."
"I'll handle organizing the research. You're good at designing the materials, so you take the presentation part."
Speaking as calmly as ever, Shia returned to her seat.
Jian headed back to hers as well, though her steps felt just a little heavier.
[2050, Jian's Room]
Midsummer.
Inside the pod, a faint trace of cool air was just enough to keep them breathing.
On the small table, the glow of the laptop cast light across the faces of the two girls.
Jian shifted in her seat.
"Find some examples of energy self-sufficient villages. I'll work on analyzing the electricity usage stats."
Her fingers moved across the keyboard with practiced ease, but her eyes kept drifting to the edges of the screen.
Beside her, Shia paused in the middle of opening a search window and looked up.
"You've been acting strange lately. Why are you suddenly so fired up about environmental stuff?"
Narrowing her eyes, Shia gave Jian a suspicious look.
"Weren't you the one shouting not long ago that air conditioning is justice?"
Jian flinched for a moment, then forced a casual shrug.
"I just… thought maybe, if I can change something, I should try."
Her words trailed off awkwardly, and her fingertips idly brushed over the laptop's touchpad.
Shia studied her for a while before tilting her head and turning back to the search window.
Then, she stopped typing again and glanced sideways at Jian.
"By the way… Jian."
"Yeah?"
"What do you think of Ji-hyuk?"
Jian's fingers froze.
On the screen, the cursor blinked over the motionless text.
"Why do you ask, all of a sudden?"
"No reason. It's just… you didn't bring up partners today. If you had, you could've ended up in the same group as Ji-hyuk."
Shia's tone was as calm as ever, yet there was a subtle undercurrent in it—something Jian couldn't quite name.
Jian tucked her hair behind her ear and looked away.
"…No, it's not like that…"
She forced a small smile. Her lips curved upward, but her eyes wavered.
"It's just… my eyes keep wandering to him. I don't know why."
Shia said nothing in response.
She kept her gaze on the laptop, though every so often she cast a brief glance toward Jian—
and in the quiet of her own thoughts, she murmured to herself.
'So it's true… her eyes really do wander to him.'
Shia lowered her head slightly, a gentle smile playing on her lips.
It was a small, quiet smile—
not big enough to tease, not awkward enough to embarrass,
simply the smile of someone who had just realized something.
"Alright. Then I'll start with the data on the Haesong Pilot Complex."
Tossing the words out lightly, she turned back to the search window and began typing in the keywords.
Jian, without replying, stared at the screen for a moment before her once-still hands began moving again.
Outside, the air was still heavy with heat, and inside the cooling pod, only their breathing and the soft tapping of keys filled the space.
In that small room, something unseen was quietly beginning to grow.
A little later, while Jian stepped out to get some water, Shia happened to glance at her laptop.
Off to one side of the search window, an odd-looking browser tab caught her eye.
"Conversation Session Log 001 – Kim Su-yeon (2023.09.14)"
Her eyes froze on the words.
At first, she meant to scroll past without a second thought—
but before she knew it, she had clicked on the tab.
Just beneath the title, the word Environmental Contest caught her attention and held it there.
'Maybe she just found this while researching for the project?'
Shia tried to convince herself, her fingers hovering still over the touchpad.
But her curiosity only grew stronger.
Slowly, she moved the cursor.
She didn't even click, yet a fragment of what looked like a chat log with the past was already visible on the screen.
'2023… It's just some kind of AI simulator. That's all it is. Right?'
She wanted to believe that.
Just then, footsteps sounded in the hallway outside, drawing closer.
Jian stepped back into the room, a cup of water in hand—
and froze when she saw Shia looking at her laptop screen.
The cup shook in her grasp, sending a few drops of water splashing onto the floor.
"Why… why is that open? You're not supposed to see that."
Jian's voice trembled.
Shia slowly tore her gaze from the screen and turned toward her.
Her eyes were unsteady, a mix of disbelief and the kind of fear that comes when you desperately want something not to be true.
"Why are you reacting like this, Jian? What… what is this? Is it real? Did you actually talk to someone from 2023?"
Jian hastily set the cup down on the desk and snapped the laptop shut.
Her fingertips felt ice-cold, and her mind was suddenly, utterly blank.
But she already knew it was too late.
Jian buried her head in her hands, fingers clutching at her hair.
"No, I… I swear I didn't mean any harm… I wasn't even sure… I mean, I thought maybe it was real, maybe not… and if I told anyone, they'd think I was crazy, so I just… I just—"
The words tumbled out in a jumble, tripping over each other before they could form a coherent thought.
Shia watched her for a moment, then drew in a slow breath.
Stepping closer, she rested a hand on Jian's shoulder.
"Calm down, Jian," she said gently.
"I'm not here to get mad at you. I was just… surprised. Anyone would be."
Jian looked up at her, bewildered, tension and fear still clouding her eyes.
Shia tilted her head slightly and went on.
"But… you were acting weird that time too, remember? In front of the school store, staring at the shared tumbler poster."
Jian flinched and looked away.
"Th-that was just… I thought it was a coincidence… no, I did think it was a coincidence, but then… actually—"
Seeing that Jian was about to spiral into another jumble of words, Shia lifted a hand in a gentle gesture to stop her.
She couldn't quite believe everything just yet, but she could tell Jian wasn't lying.
Dropping into her chair, Shia rested her palms on her knees.
"Alright.
I still don't fully understand what's going on… but let's just calm down for now.
It's fine. Just… tell me slowly, from the start."
Only then did Jian take a deep breath and give a small, hesitant nod.
A heavy silence settled between them.
Shia turned her eyes back to the laptop screen, slowly reading through the chat log.
"…This Su-yeon person," she murmured.
"If it was 2023… she'd be an adult by now."
She paused, then lifted her head to look at Jian.
"But if she really acted on what you told her… then that small change back then is standing right in front of us now."
Jian gave a quiet nod.
Shia drew in a deep breath, then let it out slowly.
"Then this isn't just some school project. This is… the future you've changed."
Jian pressed her lips together, saying nothing.
Where fate ended and their own interference began, they couldn't tell.
But one thing was certain—something had changed.
[Evening, 2050 – Ji-hyuk's Apartment]
Late at night, a faint glow from the cooling pod spilled out across the darkened hallway.
Ji-hyuk sat quietly at the desk in his small studio.
Outside the window, the soft whir of electric cars faded and returned, over and over.
Inside, the room was steeped in silence.
After rinsing off with cold water, he tossed aside an empty cup noodle container with a motion as hollow as the space it left behind.
For a long while, Ji-hyuk sat there doing nothing at all, his eyes fixed blankly on the dark, lifeless laptop screen.
Brrrrrr.
Brrrrrr.
The terminal, which had seemed asleep, began to ring.
A vibration that felt both unfamiliar and familiar at once.
He hesitated for a moment before looking at the name glowing on the screen.
[Noona]
Ji-hyuk pressed the call button without a word.
The voice that came through after so long was soft, almost tentative.
"How have you been? Sorry for calling out of the blue."
Ji-hyuk drew in a quiet breath instead of answering.
After a brief pause, his sister continued.
"Dad's… been talking about you a lot lately. He worries about you."
At that, Ji-hyuk slowly turned his head.
With an indifferent expression, he glanced at a photo of their mother hanging in the corner of the wall.
His lips twisted upward—not in amusement, but in something closer to disdain.
"Worried? He hasn't called me once.
…Just tell him not to bother. Worry that's only words doesn't mean anything."
His sister fell silent.
She'd gone through the trouble of calling, but this was the response she'd expected.
"Ji-hyuk… I just wanted to say I hope you're doing alright.
That's all. Even if it's hard, don't try to carry everything by yourself."
Ji-hyuk lifted the phone away from his ear, holding it in midair for a moment,
then slowly brought it back beside his face.
"…What does it even mean to be 'doing alright'?
How am I supposed to live to fit that?
Am I the only one struggling like this?
Why do you and Dad act like nothing's wrong? Mom is…"
His voice was quiet, but the weight of old wounds pressed heavily within it.
His sister didn't answer.
Only a short—very short—breath came through the receiver.
"Alright. I won't ask anymore.
But… call me first, someday. I'll be waiting."
Click.
Even after the line went dead, Ji-hyuk couldn't bring himself to set the phone down.
The air in the room felt frozen, like time itself had stopped on the small screen.
Slowly, he lowered his head, leaning his forehead against his arms on the desk, exhaling.
"…What did it mean… to be 'doing alright'?"
That night, the air in Ji-hyuk's room stayed warm far longer than the silence should have allowed.