Noh Go-Jin (Kim Jae-Wook) is the most popular mathematics instructor in the private education field and he is the CEO of GOTOP Education. Even though he has only a high school level education, he has achieved all of his success due to his extreme intelligence. He seems like a perfect man with a handsome appearance, high IQ, and wealth. He is also narcissistic. One day, he is suddenly warned that he will be murdered.
Lee Shin-A (Krystal) works as Noh Go-Jin’s secretary. She is a diligent and responsible employee. Due to her quiet and introverted personality, she has little presence with her boss Noh Go-Jin and her colleagues at work. Her colleagues begin to recognize her, because she has worked for the notorious Noh Go-Jin for more than 1 year. She then learns that she does not have much time left to live.