After her older brother heroically defended Sei Ohtori, Ran Kurono was determined to become the first knight under the next Ohtori family head. In order to achieve her ambition, she kept her gender a secret, but she faced fierce competition from eleven lower knights with ill intentions. Additionally, Sei had to demonstrate her suitability as the family leader. At Saint Locks Academy, both Sei and Ran underwent trials and received help from Ibara Tennou, Sei's unrefined fiancé. Despite being a position that had been passed down through the generations of the Kurono family, the competition for First Knight was intense.