Choi Yoomi is your typical Korean nerd, who is bullied by the school queenkas. 

But, she tells her brother, her only remaining family, otherwise. She tells him about how popular she is at school, and how many people want to be her friend. He believes her; why would she lie?

What he sees is a strong, happy girl; his little baby sister. He doesn't know her dark secret. He doesn't see the dark side of her.

Kim Myungsoo does. What he sees, is not a cheerful school nerd, he sees her darker side. 

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~Characters~

Choi Yoomi - she's the nerd everybody at school avoids. The school queenkas enjoy bullying and tormenting her. Yoomi keeps a secret from her older brother, as she doesn't want him to worry about her.

Choi Minho - Yoomi's older brother. He is sweet, and caring. He is very protective of his younger sister, and still sees her as a baby. Their parents died, so he has to support the two of them. He, though a caring brother, is oblivious to the things happening to his sister.

Kim Myungsoo - he is one of Yoomi's classmate. He's quiet and nobody really notices him. He is quite gothic. He is curious about Yoomi, as he knows one of her dark secrets. One can say, he has a minor crush on her.

Jung Nara - Forensic Pathologist

Detective Kim - Detective

Detective Jung - Detective

(there are more minor characters)