The protagonist Tachibana Sachiko (Nozomi Sasaki) vows to take revenge on Hanai Reina (Nagisa Shibuya), a monster as ruthless as a demon. In high school, Sachiko was teased as the "daughter of a murderer", and Reina became her only companion. However, behind Reina's angelic smile, there is a face of a murderous demon who kills easily. Reina accused Sachiko and her father of murder, and also took Sachiko's father's life. 14 years later, Sachiko, whose appearance and past have all changed, confronts Reina, who has become a new mother, again. "Let her taste the taste of living hell", Sachiko enters Reina's family as a nanny. Can an ordinary person who devotes his life to revenge drive the monster to destruction? A heroic revenge drama with repeated setbacks and entanglements begins.