Shira Reika, the daughter of a rural nobleman, is a maid in the harem who serves Shizuran, a candidate for the empress of Chaoyang. On the night of the full moon in mid-spring, while trying to save the emperor Tenyo, who was about to fall into the pond in the harem, they both fall into the pond, and when they wake up again, they find that their bodies have been switched. The solution presented is to "try to fall into the pond together again on the next full moon night," and until they can carry it out, they decide to live in a state where their bodies have actually been switched!Originally, Reika became the emperor (the body) through an accident, but it turns out that Tenyo herself is being looked down upon by the candidates for the empress because the empress, Hidemasa, is too strong. Set out to improve this, Reika devises the "Empress Guffun Plan," but...?