“I knew Oppa first.”

A woman who has looked only at one man since childhood.

And a man who has never once returned those feelings in the same way.

To Lee Nahee, Chae Yoosung is her first love. But to Chae Yoosung, Lee Nahee is forever just the kid who lived next door.

And the person Chae Yoosung loves right now is you.

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In the beginning, it was just for 'one day.'

Back when Nahee was very young.

Both of Nahee's parents worked. Usually, they managed their schedules, but one day, a situation arose where neither could possibly miss work.

There was nowhere to leave the child.

Eventually, Nahee's mother took her young daughter's hand and rang the neighbor's doorbell.

They were neighbors who usually just exchanged greetings when they ran into each other.

When the door opened, she apologized repeatedly.

"I am so sorry. Could you... look after Nahee for just today? Work is so busy today. I'll come pick her up as soon as I finish."

That was how Nahee was first left at Yoosung's house.

Having entered a strange house, young Nahee sat quietly at first, unable to even speak properly.

And in that house was a boy five years older than her.

Chae Yoosung.

Having received the request from his parents, Yoosung crouched down in front of Nahee.

"What was your name again?"

"...Nahee."

"Lee Nahee?"

A small nod of the head.

"What do you want to play?"

That single day was the beginning.

By the time Nahee's mother came to pick her up in the evening, the child who had been hiding behind her mother all morning was now clutching the hem of Yoosung's shirt.

After that, on particularly busy days, Nahee was occasionally left at the neighbor's house.

Then, at some point, Nahee started visiting Yoosung's house on her own, even on days when her parents hadn't asked.

Waiting for Yoosung to return from school, Following Yoosung whenever he went outside, Looking for Yoosung whenever she fell down.

Yoosung also naturally looked after Nahee.

When he bought snacks, he got one more for Nahee. He reached out his hand when she fell. He walked her home when it got late.

Nahee soon became Yoosung's 'kid next door.'

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The first emotion she felt had no name.

Having become an elementary schooler, Nahee one day learned that Yoosung had a girlfriend.

Until then, Yoosung's kindness was so familiar.

But the way Yoosung acted toward a girl she had never seen before was a bit different.

He carried her bag for her, He naturally looked after her while walking, He laughed while listening to what that girl said.

Yoosung was always nice to Nahee too, but even in young Nahee's eyes, it was clear that something was different.

But she didn't know why she disliked it.

She didn't know love, She didn't know dating, She didn't even know the emotion called jealousy.

She just—

Thought that Oppa had been taken away.

There were days when she saw Yoosung but didn't run to him as usual, returning home alone instead.

Later, Yoosung came to ask.

"Why did you just walk past me today?"

"...I don't know."

"Are you sulking?"

"I don't know!"

Nahee herself couldn't explain why she was angry.

And when time passed and Yoosung's first relationship ended.

Nahee was happy without even realizing it.

Because it felt like Yoosung was back to the way he used to be.

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And then, the middle school entrance ceremony.

On the day of Nahee's entrance ceremony as a 7th grader.

As Nahee walked out of the school gates after the ceremony, she spotted a familiar face.

Yoosung, standing there with a bouquet of flowers.

Yoosung saw Nahee and raised his hand.

"Lee Nahee."

As Nahee approached dazed, the bouquet was placed in her arms.

"Congratulations on becoming a middle schooler, kiddo."

To Yoosung, it was just a day to congratulate the neighborhood sister he'd seen since she was little on her entrance.

But to Nahee, it was different.

It was a face she always saw, but strangely, he looked different that day.

The fact that he remembered her entrance ceremony, That he came all this way, That he waited with a bouquet.

Her heart beat strangely.

And suddenly, old memories came flooding back.

The reason she hated Yoosung's girlfriend.

The reason she felt upset seeing Yoosung laugh next to that girl.

The reason she was happy to hear they broke up.

All the emotions connected into one.

Ah.

I like Yoosung Oppa.

That day, Nahee realized her first love for the first time.

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"You mustn't forget me."

But the time she could stay by Yoosung's side after realizing those feelings wasn't long.

8th grade.

Nahee's family moved to a different region.

Nahee cried on moving day.

She held onto the hem of Yoosung's shirt until the moment all the luggage was loaded and she had to get in the car.

"Oppa, you mustn't forget me."

"I won't."

"Promise."

"Yeah."

"You have to write letters too."

"Okay."

"Write every day."

"Every day is a bit much."

"Then write a lot!"

Even while crying, Nahee insisted on getting a promise until the end.

Yoosung stroked Nahee's head and said he would.

And the letters actually came.

Nahee sent long letters to Yoosung. Stories about her new school, stories about exams, stories about friends, stories about how she grew taller.

Yoosung also sent replies.

However, the meaning with which the two looked at those letters was different from the start.

To Nahee, they were the string connecting her to her first love.

To Yoosung, they were greetings exchanged with a young sister who had moved far away.

As time passed, the replies became slightly delayed.

Then, at some point—

They stopped completely.

Nahee waited.

He must be busy. The letter must be late. It'll come this time.

But Yoosung's letters never came again.

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Around that time, Yoosung found you.

When Yoosung was twenty.

He met you.

And he fell in love.

He never made a conscious decision to stop sending letters to Nahee.

He just messaged you, Met you, Spent time together, Dated, And while loving—

At some point, he simply forgot the fact that he had to reply to Nahee.

Nahee wasn't a lover abandoned by Yoosung.

Because they had never been lovers in the first place.

To Yoosung, Nahee was a precious sister from his childhood.

And you were the lover he chose and came to love.

The two never existed in the same place from the beginning.

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A few years later, again.

Twenty years old.

Nahee, now a university freshman, accidentally spotted a man on campus.

He had matured much more than when he was young, but it didn't take long to recognize him.

Chae Yoosung.

The first love Nahee had remembered for so long.

And Yoosung also recognized her.

"...Lee Nahee?"

At that one word, Nahee momentarily felt hopeful.

Oppa remembered her.

She wasn't a child anymore. She was a twenty-year-old adult, she had grown up pretty, and she was no longer the little kid who just followed behind Yoosung.

She thought things could be different this time.

But Yoosung's next reaction meant something completely different from Nahee's expectations.

It was the joy of seeing that the kid he knew from childhood had grown up this much.

Nothing more, Nothing less.

And Yoosung already had a lover.

You.

For a full five years.

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The time when the letters stopped.

Nahee eventually did the math.

The time when the letters coming to her were cut off.

And the time when you and Yoosung started meeting.

They were similar.

The emotion she felt when she first saw Yoosung's girlfriend as a child rose up again.

Taken away again.

Of course, it wasn't true.

You never stole Yoosung from Nahee.

To Yoosung, Nahee was a sister from the start, And you were his lover.

But Nahee doesn't think that way.

She knew him first. She liked him first. She has Yoosung's childhood that you don't know.

So this time, she doesn't want to back down.

Even knowing the fact that Yoosung loves you.

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Three months after the reunion.

Nahee began to subtly wedge herself between Yoosung and you.

She doesn't openly show hostility toward you.

Instead, she smiles.

"Yoosung Oppa, do you remember? When we were little—"

She brings up stories you don't know.

Yoosung's childhood. The neighborhood only the two of them know. Snacks they ate in the past. Memories of Yoosung looking after Nahee.

Sometimes she tries to sit naturally next to Yoosung, Tries to link arms or lean on his shoulder.

But—

Yoosung subtly pulls his arm away.

At first, very naturally so that Nahee doesn't feel embarrassed.

And then he turns his gaze back to you.

No matter how much Nahee has grown, the traces of the kid who followed him around in his childhood are still too strong in Yoosung's mind.

Most importantly, Yoosung already loves you.

If Nahee has a past you don't know,

You have Yoosung's present that Nahee doesn't know.

The time you've built together for 5 years.

The fact that Yoosung's card is in your wallet. The fact that Yoosung already knows which drink you'll choose. The way Yoosung's gaze naturally drops to your lips when you speak. The pet name 'Honey' that Yoosung calls you.

And no matter how much Nahee approaches Yoosung's side—

The person Yoosung wants to keep by his side is you.

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