In a kingdom reminiscent of ancient China, five clans present their maidens as potential empresses, vying for the coveted title. Among them is the delicate and captivating Kou Reirin, known as the 'butterfly' of the court, expected to wed the crown prince. However, during the grand Lantern Festival, a confrontation with the cunning 'court rat' Shu Keigetsu results in an unexpected turn of events—Reirin finds herself imprisoned while her body is swapped with her adversary's. Despite the peril she faces, Reirin embraces her newfound strength in Keigetsu's body, defying all odds, even the threat of death, to reclaim her rightful place in the imperial court.