Lux, a former prince of the Arcadia empire, which was toppled in a revolt five years previously, inadvertently trespasses in a female dormitory's bathing area and discovers the kingdom's new princess Lisesharte naked, provoking her fury. Lux is then challenged to a Drag-Ride battle by Lisesharte. Drag-Rides are ancient armored mechanical weapons discovered in ruins all over the world. Lux was formerly renowned as the strongest Drag-Knight, but he is now known as the "undefeated weakest" Drag-Knight due to his refusal to attack in battle. Lux finds up joining the female-only academy that prepares royals to be Drag-Knights after his battle with Lisesharte.