In the kingdom of Ei, the Maiden Court is located within the palace's inner court, whose purpose is to nurture the next empress and four imperial consorts from five prominent clans. The crown prince's favorite is the virtuous Reirin Kou, excelling in every task she is given despite her sickly constitution. In contrast, Keigetsu Shu is considered a hindrance due to her ill-mannered conduct. While Reirin is a graceful butterfly beloved by all, Keigetsu is a sewer rat no one dares to look at.

During the Double Sevens Festival, a jealous Keigetsu attempts to murder Reirin by pushing her off a balcony. Fortunately, Reirin is saved from an untimely death, whereas Keigetsu is imprisoned and awaits her punishment. Unbeknownst to all, Keigetsu has used forbidden magic to swap bodies with Reirin, wishing to have Reirin's perfect life.

However, not all goes according to Keigetsu's plan, as Reirin's weak body obstructs her evil schemes. At the same time, Reirin enjoys Keigetsu's physically fit build. Being unbound by rules, Reirin takes on the mission to live by playing the role of a villainess, no matter how inept she might be.

[Written by MAL Rewrite]