The “Nestling Court,” a court where princesses from the five clans are gathered in order to raise the next empress. Reirin, a frail Nestling who is often called the next empress and is as beautiful as a butterfly, ended up switching bodies with the Nestling who is jealous of her, Keigetsu! Suddenly, Reirin is hated by everyone around her and called the Rat Princess. She is put into a horrible environment where no one trusts her and she’s despised by the people who have always been kind to her, but… “I’m not out of breath, and I don’t faint… What a healthy body! I, I’m so jealous…!” Reirin, the one who everyone envies, is a person with a steel mentality who has been battling death all her life——!?