In the six years since Hwang Ah-joong's real mother came back into her life, the only time she's ever seen her looking so vulnerable was when they'd discussed the reason she was put up for adoption. Jo Kangja was no pushover of a woman, though she'd given up her first child, she'd had all the right reasons to do so. Ah-joong didn't blame her, not when Kangja was the one to reach out to her when she turned fifteen.

It was shocking to learn the fate of her biological father and the manner in how he died, but she learned to deal with it. Jo Kangja was brave to have come forward and told her the truth. The scars she carried were worse than hers, and the parents Ah-joong received in her absensce were everything she could ever ask for.

Though her father's work wasn't what people would call 'respectable', he gave them a good life and protected them from his enemies. They lived in an extravagant home and owned nice things, things other kids in her classes didn't own. He gave more than she could ever have asked for. The only thing he couldn't protect them from was illness, and despite all the money and treatment he spent to save her, her adoptive mother ultimately died of heart complications.

Hwang Jihoon was the best father Ah-joong could ask for. He tolerated her attitude, protected her, loved her, and bailed her out whenever she caused trouble-- which was often. Ah-joong, though twenty now, has yet to graduate from high school. Like her biological mother and adoptive father both, she has a knack for getting into sticky situations. Ah-joong was held back twice and even attended remedial school to 'better her attitude', as the teachers called it.

When Kangja suddenly calls her up asking to speak with her father, Ah-joong knows something is wrong. Her mother isn't the kind of person ask for help of any kind, especially not to Jihoon, the man she feels indebted to for raising Ah-joong. But her mother's voice doesn't sound like normal and when she arrives, she seems weaker, though Ah-joong can feel her determination as she marches into Jihoon's office and closes the door behind her.

Ah-joong knows she shouldn't listen, but she does and learning the story behind her half sister's hospitalization, she can understand Kangja's fury. She asks her father to look into the things happening at Myeongseong High School and to assign someone to keep an eye on Ah-ran. Jihoon easily agrees. Although Oh Ah-ran is not his daughter by any means and the two half-sisters aren't close, their resemblance is impeccable and he definitely considers her family.

Her father tells Kangja that looking into the school will be difficult, but he'll find a young recruit to go undercover there and look into things. That's when Ah-joong decides. She's intended to transfer into a new school to finish her final year anyway, and what better way to start of the year than to crush the little twerps who dared to harm her sister?