The fierce survival and success of a female slave in the Joseon Dynasty, and the story of a woman whose name, identity, and even her husband were all fake.

A seemingly ordinary working mother secretly lives as a legendary sniper who delivers justice where the law fails. After returning from a three-year hiatus, she must balance protecting her family with eliminating dangerous criminals, all while a determined journalist and a relentless detective close in on her hidden identity.

Every last Thursday of the month at an all-girls high school, the students of Class 2–5 cast their votes in a popularity poll. The results classify them into Grades A, B, C, D, and F. If they fall into Grade F, they become legitimate victims of school violence.