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Strong Hearts: The Legacy of Do Sisters- By: Tina Marie


Chapter 9 - Subject Zero

Last Updated on 2025-06-09 21:53:47

The sun hadn’t even risen yet, but the Doom Den was lit like a war room.

Do Rin had her laptop cracked open, three portable drives connected, and one mission in mind:
Find out who Subject Zero was.

Across from her, Do Rae paced with a slice of cold pizza and a thousand questions burning a hole in her skull.

Jin Seok leaned against the wall, still visibly stunned. He hadn’t said much since the fight. Just the occasional deep sigh like “Did I really just see that girl body slam a genetically modified guard?”

He finally broke the silence.

“So let me get this straight… you two have superhuman strength, your mom used to fight crime in secret, your aunt went rogue, and now a tech company is using your DNA to build black-market super soldiers?”

Rae: “Yeah, that about covers it.”

Jin Seok blinked. “Okay. Cool. Just making sure I’m still in reality.”


Rin cut in. “Guys. I found something.”

She turned the laptop toward them.

SUBJECT ZERO
Name: Unknown
Status: Terminated
Year: 2003
DNA Match: 98.7% match to Do Bong Soon
Condition: Irreversible cognitive damage. Partial success.

Rae leaned in. “What does ‘partial success’ mean?”

“It means they made someone strong,” Rin said, “but broke their brain doing it.”

Jin Seok pointed at the match percentage. “That’s… almost identical to your mom.”

Rin nodded. “Because Subject Zero wasn’t just a random test subject.”

She clicked on a subfile: a distorted photo of a young woman. Face blurry, timestamped, locked behind red tape.

“She was the first artificial strong woman.
And I think… she might’ve been related to Mom.”


Flashback — 2003.

A hidden lab.
Steel tables. Glass rooms.
A young woman thrashing in restraints, crying, then screaming—until her voice broke.

Standing behind the glass?

Do Mi Na.

She whispered, “She’ll survive. She has to.”

And when someone asked for her name?

“She has no name,” Mi Na said.
“She’s the proof.”


Back in the present, Rin’s hands were shaking.

“Blue Star isn’t trying to copy us,” she said. “They’re trying to finish what Mi Na started. Fix her mistake. Make the formula stable. And they think we’re the key to doing it right.”

Rae looked at her sister.

“We need to find Subject Zero. If she’s alive… she’s proof they’re lying to the public.
And she didn’t ask to be made. She deserves to be saved.”


Suddenly, Rin’s screen pinged.

A location file. A security log from three weeks ago.

SUBJECT ZERO — MOVED TO OFF-SITE HOLDING
Destination: Facility X13 – Busan

Rae’s eyes lit up.

“Road trip?”

Other Chapters
Characters
  • Do Rae
    Do Rae

    (18 years old) Fiery, bold, athletic, often acts before she thinks. Hates being compared to Bong Soon.

  • Do Rin
    Do Rin

    (18 years old) Observant, tech-savvy, introverted, feels overwhelmed by the family legacy.

  • Jin Seok
    Jin Seok

    (22 years old) Rookie police officer, Do Rae’s love interest, brave but clueless about her strength.

  • Kang Jae
    Kang Jae

    (21 years old) Hacker with a criminal past, Do Rin’s love interest. Tied to the villain’s network.

  • Do Bong Soon & An Min Hyeok
    Do Bong Soon & An Min Hyeok

    Bong Soon is older, wiser, still powerful, juggling motherhood and her own past enemies. Min Hyeok is a doting dad, now a CEO of a global tech company with secrets buried deep.