After executing a man in front of his daughter, Haegu takes the child under her wing and names her Mian, which means "sorry" in Korean. Haegu gives Mian one mission: "Kill me when you can." Mian intends to achieve this through feigned love and emotional manipulation.
But as Mian grows into an adult, her plan for revenge turns into confusion as she develops feelings of lust and possibly even love for Haegu. Meanwhile, Haegu struggles with her own feelings for Mian while continuing to carry out deadly missions. Will Haegu and Mian ever be able to truly love each other, or will they remain trapped in their cycle of violence and revenge?
