Lux, who was once the strongest Drag-Knight, earned the title of "the weakest undefeated" because he never actively attacked others. Five years ago, he witnessed the destruction of his country due to revolution. However, when he accidentally broke into the bathhouse of a women's dormitory, he unexpectedly met Lizsharte, the princess of the New Kingdom, and later inexplicably entered a girls' school that trained Drag-Knights. The story of the weakest prince's harem battle began.