The Katjvarna Empire is in the midst of a war with the Kioka Republic, and is currently engaged in a defensive tactic to protect their borders from enemy attacks. Yatorishino, belonging to a notable family in the empire, is preparing for the high-ranking officer exams. To ensure her success, she persuades Ikuta, a carefree womanizer with an aversion to war, to join her and assist in exchange for a favor from her influential family. The first written test proceeds smoothly, and they embark on a boat for the subsequent one. However, the boat ends up sinking, stranding Yatorishino, Ikuta, several other exam takers, and an enigmatic, valued young girl behind enemy lines.
