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The first time 004 picked up Yoo Dayun from school, three boys tripped over themselves trying to hold the gate open for her.
He noticed.
004 noticed everything that could become a problem.
He leaned casually against the brick wall across from the entrance, dressed in simple black, hands in his pockets. He looked almost normal—if not for the way his eyes tracked movement like he was calculating distance, speed, intent.
Students gave him space without understanding why.
Dayun spotted him immediately.
“Oppa’s friend!” she called softly, walking toward him with that gentle brightness she carried despite everything she’d been through.
He straightened.
“…004,” he corrected automatically.
She smiled. “I know.”
There was no fear in her eyes.
That always confused him.
The boys who had been hovering near her slowed when they saw him.
“Who’s that?” one whispered.
“Is that her boyfriend?”
004’s head tilted.
Boyfriend?
He felt something sharp and irritated rise in his chest.
He stepped forward.
The boys froze.
004 looked at them the way he would look at a target before deciding which artery to cut first.
Calm.
Interested.
Slightly bored.
“Problem?” he asked annoyed.
They shook their heads so quickly one nearly dropped his bag.
“No, hyung!”
Hyung.
He wasn’t their hyung.
But he let it slide.
They left.
Quickly.
Dayun blinked up at him. “You didn’t have to do that.”
“I didn’t do anything.”
“You scared them.”
He shrugged. “Good.”
He walked half a step behind her as they left school grounds.
Always behind.
Always angled.
So if something came from the front, he could reach her in one second.
If something came from the side, half a second.
If something came from behind—
His jaw tightened slightly.
It wouldn’t.
.
.
.
.
.
A month later, another boy tried to follow her after cram school.
004 was already there.
Sitting on a bench across the street.
Eating fried chicken from a paper box.
The boy approached Dayun nervously.
“Um… I just wanted to ask if—”
004 appeared beside him without a sound.
The boy nearly screamed.
004 took another bite of chicken.
“…She’s busy.”
The boy stared at him.
“I—I just wanted to—”
004 swallowed slowly.
Then leaned close enough that the boy could see the faint, thin scars lining his hands.
“Do you want your kneecaps to continue functioning?”
The boy bolted.
Dayun stared.
“…You can’t threaten every boy.”
“Watch me.”
She sighed dramatically.
But she was smiling.
That night, Ijin returned from his mission.
He found 004 sitting on the edge of the rooftop, silent.
“Report,” Ijin said calmly.
004 didn’t look at him.
“She’s fine.”
Ijin’s eyes studied him.
Closed briefly.
Peaceful.
“…Thank you.”
004 clicked his tongue.
“Don’t misunderstand.”
“Mm.”
“She’s small.”
“I know.”
“She doesn’t see danger until it’s close.”
A pause.
“She sees good first,” Ijin said quietly.
004 didn’t respond.
He thought about Dayun’s laugh.
The way she looked at him without fear.
“…I’ll keep watching,” he muttered.
Ijin looked at him for a long moment.
Then—
“I trust you.”
Those words hit harder than any punch.
004 scoffed, standing.
“Don’t get sentimental.”
But he stayed on that rooftop a little longer that night.
Watching the street below.
Just in case.