Taehyung, Jungkook, and Y/N are step-siblings living together in a grand mansion in Seoul. Their parents passed away in an accident when the boys were just 18 and Y/N was only 10 at the time. Now, Taehyung and Jungkook work as strict university professors. Though they have a stern demeanor, they deeply care for Y/N. She finds them a little intimidating at times. And she has crush on her step brothers but never shows.Y/N is a clumsy, innocent, yet mischievous girl who often gets herself—and others—into trouble.

The morning sun peeked through the curtains of Y/N’s room. It was 7 AM when Jungkook quietly stepped inside. His soft footsteps barely made a sound on the floor as he walked up to the bed where Y/N lay bundled in her blankets, peacefully asleep. Leaning down, he pressed a gentle kiss to her forehead.

"Wake up, baby," Jungkook whispered softly.

Y/N groaned, burying her face into the pillow. “Five more minutes, oppa,” she whined in a sleepy voice.

“No, get up. You’ll be late,” Jungkook said, his tone firmer now.

“Please... I don’t wanna go,” Y/N mumbled, tugging the blanket over her head. “Let me sleep.”

Jungkook’s voice suddenly turned stern. “Get up, Kim Y/N. Or do you want punishment?”

Her eyes shot open immediately. Sitting up straight in bed, she stammered, “I-I’m awake, oppa...” Her big, doe-like eyes were wide in fear.

Seeing her expression, Jungkook chuckled and pulled her into a quick, warm hug. “Aigoo, my baby’s scared now?” he teased softly, ruffling her hair. “Come on, get up and come downstairs. Breakfast is ready.” With that, he left the room.

Y/N quickly scrambled to the bathroom to freshen up and then dashed out, her footsteps light and hurried on the stairs.

But just as she reached the last step, a cold, sharp voice echoed through the hallway. “How many times have I told you not to run on the stairs?”

She froze. Her eyes found Taehyung at the end of the corridor, arms crossed, eyes narrowed and face unreadable.

“S-sorry, oppa...” she muttered, lowering her gaze and slowly walking toward the dining table.

Taehyung sighed quietly, watching her retreating figure. This kid… always knows how to test my patience, he thought to himself.

He placed the breakfast neatly on the table just as Jungkook came downstairs, fully dressed and smiling with his usual bunny grin. “Good morning, everyone!”

“Good morning,” Taehyung responded with his usual cold tone.

Y/N’s eyes wandered to the table, and her smile vanished. Her lips pushed into a pout. “Vegetables? Again? I don’t want these, oppa… Can I have pancakes instead?” she pleaded, blinking rapidly and trying her best puppy-eyed look.

“Don’t,” Taehyung said firmly, not even looking at her. “That won’t work on me. Eat what’s there and get ready for college.”

She sat down with a defeated sigh. Why is he always so strict with me? she wondered, her pout still present.

“Please…” she tried once more, voice low and hesitant.

Taehyung’s jaw clenched slightly, frustration creeping in. Before he could speak, Jungkook stepped in gently. “Y/N, eat this. It’s really good, you know? Hyung woke up early to cook for us. Isn’t it unfair to ignore someone’s effort like that?”

Y/N looked from Jungkook to Taehyung, whose face looked more tired than usual. She realized he had been handling a lot—CEO duties, university lectures, and even cooking for them. Her eyes softened. Though bratty, she was sensitive at heart.

Silently, she picked up her chopsticks and started eating.

Jungkook smiled at her and gave a small glance toward his older brother. Taehyung, though quiet, kept his eyes on Y/N as she ate without a word.

After breakfast, the three of them left for university together. The car ride was mostly silent. Y/N stayed quiet for the most part, occasionally talking to Jungkook—he was the only one who treated her gently most of the time.

Flashback — 8 Years Ago

The heavy rain poured down over the city of Seoul the night everything changed.

Eighteen-year-old Taehyung and Jungkook sat side by side in the sterile hospital corridor, drenched, silent, and trembling. The world around them had gone quiet, except for the constant beep of machines and the echo of rushing nurses.

Their parents were gone. Just like that. A single car accident had shattered everything.

But what broke them even more was the sight of little Y/N—barely ten, sobbing in her oversized hoodie, clinging to Jungkook’s arm like her life depended on it. Her face was stained with tears and confusion. She kept asking, “Where’s mommy? Where’s dad?” But there were no answers left to give.

From that moment, something inside both boys shifted. They weren’t kids anymore.

Jungkook was the first to speak that night. “We have to protect her now.”

Taehyung didn't answer, just clenched his fists. I won’t let her go through what we did. Never.

Years Later

Life after that was never easy. While people around them gave fake sympathies, their relatives only cared about inheritance. Fake smiles, betrayals, backstabbing… It hardened them. Especially Taehyung, who saw firsthand how vulnerable kindness could be.

He watched Y/N grow—sweet, trusting, fragile. Just like her mother had been.

Taehyung became stricter with her not because he didn’t love her, but because he did—too much. He feared the world would eat her alive if she didn’t learn to be careful. Every scolding, every harsh tone was his twisted way of protecting her from the same pain they’d endured.

Jungkook, on the other hand, found it harder to hide his softness toward Y/N. She reminded him of warmth in a cold world, and while he tried to maintain a firm exterior, he’d often melt around her—always covering for her mistakes, always shielding her from Taehyung's icy glares.

But what neither of them would admit, even to themselves, was that somewhere along the way… their protectiveness started turning into something more.

And that scared them.

Especially Taehyung, who couldn’t afford to be weak. Not again.

She deserves someone better, he would tell himself.

But every time he saw her pout or cry, it chipped away at the walls he built.

Back in the present, as the car moved through the morning traffic, Taehyung glanced at Y/N through the rearview mirror.

She sat quietly, looking out the window, unaware of the silent storm inside her brothers’ hearts.

At the University — Morning Classes

Taehyung and Jungkook were names that carried weight across the entire university. The mere sound of their footsteps down the hall was enough to silence even the noisiest groups of students. Sharp suits, sharper eyes, and no tolerance for nonsense—they were known as the cold, untouchable professors.

No one knew about Y/N being their stepsister. It was a carefully kept secret—one the brothers insisted on. They wanted to keep their family life protected, and perhaps deep down, didn't want anyone looking at Y/N differently. She was already clumsy and playful; being related to the two most feared professors on campus would only make her a target.

Y/N walked into her class, smiling as she spotted her best friend.

"Kate!" she waved, skipping over.

Kate beamed. "Y/N! You're late again. Professor Jungkook will kill you!"

Y/N groaned dramatically. "I know... He woke me up himself! But I just—ugh—I still wanted five more minutes."

As they chatted, another presence made its way toward them—Lia.

Bee queen of the department. Always immaculately dressed, overly confident, and always lurking around Professor Kim Taehyung.

"Oh look," Lia smirked, flipping her hair, "Y/N, late again? Honestly, how are you not expelled yet?" Her eyes gleamed with superiority.

Y/N forced a smile, not wanting to start anything. "Morning, Lia."

Lia's gaze flickered toward the front of the class. "Anyway... I heard Professor Taehyung is checking assignments today. Can't wait to see him. That man in a suit is... wow. He should walk a runway instead of teaching."

Kate rolled her eyes, but Y/N stayed quiet. If only she knew, she thought.

Just then, the classroom door swung open.

Every student shot up in an instant.

Jungkook walked in with a cold expression, dark eyes scanning the room. His presence demanded respect without a word. Not a single student dared to breathe too loud.

His gaze swept the room, pausing when it landed on Y/N.

She was seated awkwardly, flipping through her textbook in panic, bottom lip jutting out in a pout.

Jungkook kept his face neutral, but his heart softened instantly. This cute little kiddo, he thought, almost chuckling—but caught himself.

Clearing his throat, he placed his laptop on the desk.

"Sit," he said, voice sharp and commanding.

The students immediately obeyed, and the lecture began.

Despite his strict tone, Jungkook's eyes often flickered back to Y/N, making sure she was keeping up—even though he pretended not to notice when she yawned or scribbled in her notes messily.

Outside, a group of students were already whispering about Professor Kim's upcoming lecture, while others discussed rumors about Taehyung's cold rejections and how he "never even looks at girls" no matter how much attention they throw at him.

What they didn't know... was that the only girl he noticed every day wasn't even on their radar.

Later That Day – Second Lecture: Professor Kim Taehyung's Class

The energy in the room shifted before he even entered.

Students sat upright, nervous hands fidgeting with pens and papers. Everyone knew when Professor Kim Taehyung was scheduled to teach — and they knew better than to test his patience.

The door opened with a soft click, and in walked Taehyung. Tall, composed, and dressed in a sharp black suit, his expression unreadable but heavy with a storm behind his eyes.

Y/N felt her stomach twist. She could tell something was off. His jaw was tense, brows slightly furrowed. He hadn't even spared the class his usual cold "Good morning." That was a warning sign in itself.

He placed a stack of test reports on the desk with a firm thud.

"The results were unacceptable," he began, voice low but filled with quiet rage. "Only 70% of you passed. That means 30% failed. If you're one of them, you should seriously reconsider your priorities."

His sharp eyes scanned the room like a hawk.

Y/N felt her heart thump wildly. Please don't say my name. Please don't—

"Kim Y/N."

Her name rang through the silence like a slap. Heads turned toward her.

Y/N froze. "Y-Yes, Professor?"

His eyes narrowed on her. Cold. Disappointed. "You failed. Again. How many chances do you expect me to give you before I treat you like everyone else?"

Y/N's lips parted, but she couldn't form words. Her chest tightened. She couldn't even look up.

Kate placed a hand on hers under the desk, but Y/N didn't respond. The sting of his words hurt more than she expected — and she didn't understand why.

Just then, the silence was broken by a too-sweet voice.

"But Professor Kim... maybe she was just distracted?" Lia said, standing up from her seat with a flirtatious smile. She flipped her hair and slowly walked toward the front. "I mean, not all of us can be as smart as you."

The whole class held its breath.

Taehyung slowly looked up from the papers, gaze icy and expression unreadable. "Miss Lia, was that your idea of helpful input or just another failed attempt to flirt with your professor?"

The room went dead silent. Lia's face froze.

"I don't care who you think you are, or what you think your charm can accomplish," he continued, voice like a blade. "This is a university. Not your personal dating pool."

Y/N blinked, surprised by how harsh he was even with Lia. She didn't know why, but a strange feeling twisted in her chest — like she was both relieved and... affected.

Taehyung didn't stop there. "If you spent half as much time studying as you do trying to gain my attention, maybe your grade wouldn't be sitting at the bottom of this pile."

Lia, embarrassed and fuming, returned to her seat without another word.

Taehyung exhaled sharply, clearly trying to contain his temper. His eyes flicked back to Y/N — briefly, just for a second. Something soft was there, just for a flicker, before it disappeared again behind his mask.

"Class is dismissed for today. Those who failed, see me in my office by 4 PM. No excuses."

As he left the room, his long coat trailing behind him, Y/N's heart pounded.

She didn't understand why his disappointment hurt more than the bad grade itself.

And she definitely didn't understand the warm ache in her chest when he scolded Lia.

4:00 PM – Professor Kim Taehyung's Office

The hallway outside Taehyung's office was dead silent.

A group of students stood anxiously in front of the large wooden door, barely able to breathe. No one dared to speak. The fear was real. Everyone had heard the rumors — that Professor Kim was a devil when it came to discipline. He didn't believe in warnings. Only consequences.

Y/N stood among them, fingers trembling, clutching her notebook to her chest. Her heart was pounding against her ribs like a drum. She could barely swallow.

Why didn't I study? Why did I stay up watching that drama? she cursed herself quietly.

The door creaked open.

Taehyung stood there, sleeves rolled up, eyes bloodshot from a long day — his expression ice-cold. In one hand, he held a thin wooden cane. His gaze swept over the students like fire.

"Inside. Now."

They moved quickly, lining up in front of his desk like soldiers awaiting judgment.

"Stand straight," he snapped. "Hands behind your backs. Eyes forward."

No one dared move. Even the usually loud-mouthed guy in class was trembling.

Taehyung slowly walked in front of the line, cane tapping lightly against his palm with each step. His voice was dangerously calm. "You think this is a joke? Failing after being given everything? My lectures, the notes, reviews — and this is how you thank me?"

He stopped in front of Y/N. She could feel the heat of his presence, though he hadn't even looked directly at her yet. Her hands were shaking behind her back. Her lips trembled slightly. Her head lowered instinctively, afraid he'd see the guilt on her face.

Taehyung's gaze lingered on her. His chest tightened — She's scared. And not just of the punishment. Of him.

He gritted his teeth, looking away.

"You," he pointed to the first student. "Step forward."

One by one, he scolded and punished them.

HIT!! HIT!! HIT!! HIT!!

The cane would slam against the shoulders or the thighs causing burn of hit , just enough to send a shock through their spines. He used fear as his weapon — and it worked.

Y/N watched every punishment, heart sinking deeper.

When it was finally her turn, she stepped forward, legs stiff. Taehyung's eyes met hers for the first time up close. Her big, tear-filled eyes stared at him. Her lip quivered.

He didn't say anything at first. The room was silent.

Then slowly, his fingers tightened around the cane — but he didn't raise it.

"You too?" he said quietly, almost bitterly. "You, out of all people?"

"I... I'm sorry, op..i .mean..pro..Professor..—" Y/N blurted, before realizing what she'd said.

Gasps filled the room. A few students blinked in confusion.

Taehyung's eyes narrowed. "Everyone, out."

No one questioned him. The room emptied in seconds.

Once it was just the two of them, he walked toward her, his expression still unreadable.

"You called me oppa here," he said quietly.

Y/N's face flushed. "I-I didn't mean to... it just slipped—"

"You think this is a game, Y/N?" His voice cracked slightly, filled with frustration. "You failed. You lied. You think I scold these kids because I enjoy it? I'm hard on them because no one was hard on us when we needed it."

Tears welled in her eyes. "I didn't mean to disappoint you... I just..."

Taehyung stared at her for a long moment, then placed the cane on the desk and looked away, voice tired. "You think it doesn't break me seeing you scared of me?"

Y/N's lips parted slightly, stunned.

He ran a hand through his hair, suddenly looking much older, much more exhausted.

"You're dismissed," he finally said, without turning back.

But as she reached the door, he added softly, "Don't make me choose between being your brother... or your professor. Because if you keep failing, I won't go easy next time. Understood?"

She nodded quickly, wiping her tears.

"Yes, Professor Kim."

And with that, she left — shaken, confused, but with a heart aching in a way she didn't quite understand.

Author:

Hello everyone!

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