Northern Seoul – Abandoned Subway Line 4 Extension

The cold air smelled like rust and old concrete.
Do Rin stepped lightly across the tracks, Kang Jae at her side, the only light coming from the flicker of his modified wrist scanner.

“You sure she’s down here?” Rin asked.

Jae nodded. “The signal’s clean. It’s not a bounce—it’s a root feed. Mi Na’s been patching herself into the city’s old neural routing infrastructure. She’s building something.”

“Or reviving something.”

Rin’s breath came out in a cloud.

She could feel the hum in the walls—low, rhythmic, mechanical. Like a pulse.

“Feels like a trap,” she muttered.

“Definitely is,” Jae said. “But you already knew that and came anyway. That’s why I like you.”

She gave him a sideways glance. “I haven’t decided if I like you back.”

“You don’t have to. Just don’t shoot me.”

Meanwhile — Yongsan District, Seoul

Do Rae stepped into the old shipping yard wearing jeans, a grey hoodie, and a Kevlar-lined bomber jacket.

Jin Seok was beside her, nervously adjusting his earpiece.

“You’re sure this place is tied to Blue Star?”

“Positive. Rin ran the node trace. Black-market strength enhancers are moving through here like protein bars. But there’s something different about this batch.”

“Different how?”

“They’re volatile,” Rae said. “Unstable. One dose could kill a normal person. But someone’s selling them to kids.”

Jin Seok swore under his breath.

They crept between crates, weapons drawn, scanning for movement.

Suddenly—a shout. A struggle.

They ran toward it.

A teen boy, maybe sixteen, was convulsing on the ground, muscles twitching violently.

A half-empty vial rolled across the pavement.

Rae knelt beside him, eyes flashing with alarm. “He’s overdosing—on strength.”

She lifted him gently, too gently for the force she was using, and handed him off to Jin Seok.

“Get him to the mobile unit. Now.”

“What about you?”

She pulled her hood up.

“I’m finding who sold it.”

And she disappeared into the shadows.

Back underground, Rin and Jae reached a sealed metal door marked with an old Legacy emblem—one Mi Na had hijacked long ago.

The scanner beeped.

“Unauthorized DNA match detected: Do Rin.”

Then the door hissed open.

Inside: silence.
And a voice echoing from deep within.

“Welcome home, little twin. I’ve missed you.”

Rin’s face hardened.

“Let’s finish this.”