Cha Yeon Jin is a high school girl whose outwardly normal existence and reticent character masks her true identity: she is a professional assassin who is seeking vengeance for her mother after watching her killed in front of her eyes. She infiltrates SS1, the secret organization that her mother was connected to, by becoming one of their killers, all the while trying to track down her mother's murderer.

Cast

Han Geu-ru

Cha Yeon-jin

Kim Jung-tae

Yoo Sung-ho

Park Hyo-ju

Min Ji-young

Baek Do-bin

Choi Tae-young

Kim Roi-ha

Jang Se-wook

Jeon Mi-seon

Cha In-sook

Jeon Kuk-hwan

Kwon Do-hwan

Kim Dong-jun

Go Young-min

Bae Noo-ri

Nal Na Ri

Kim Sa-hee

Scientist

Han Sa-myeong

[Taekwondo club member]