Lux, a former ruler of an empire called Arcadia that was overthrown by a rebellion five years ago, accidentally transfer a female dormitory bathroom area, seeing the new princess naked Lisesharte empire, causing bother. Lisesharte challenges Lux Drag-Ride a duel. Lux was formerly called the Drag-Knight stronger, but now is known as the "weakest invincible" Drag-Knight because he absolutely does not attack in battle. After his duel with Lisesharte, Lux ends attending the academy just for girls coaching royalty to be Drag-Knights.