The story begins with the protagonist, who has been reincarnated into the world of the doujin game "Record of Thanatos," finding himself as a young man named Royle, a cadet at the Imperial Military Academy. He has about thirty days until graduation and is already accompanied by Yuno, his first "Princess Unit" and a character with inexplicably high stats, particularly in combat. Royle, retaining his past life's memories and gamer knowledge, recognizes Yuno's "bugged" nature, possessing an unusually high number of skills and a combat power far exceeding any normal unit. Yuno, an orphan he found scavenging for food, is fiercely loyal to him, seeing him as her protector and the one who gave her a name. Royle's immediate goal is to recruit more Princess Units to prepare for the impending era of turmoil in the Ilias Empire, which is predicted to begin in two years.
The narrative then shifts to Yuno's past, detailing her life as an orphan in the harsh capital city. Despite her difficult circumstances, she possessed abnormal physical abilities and a striking beauty, which unfortunately attracted unwanted attention. Her ability to defend herself, often violently, led to her being feared as a "demon." Her encounter with Royle marked a turning point; he was the first to call her by name without fear, offering her food and a place by his side. This act of kindness deeply affected Yuno, solidifying her devotion to Royle.
Royle's recruitment efforts lead him to two other promising Princess Units: Claire and Cynthia. Claire, a talented warrior from a humble background, harbors a deep resentment towards the nobility due to their mistreatment of commoners. She joined the military academy with the ideal of protecting the weak and curbing noble arrogance, only to become disillusioned by the corruption within the military itself. Her promising future was jeopardized by a powerful noble she had previously confronted. Cynthia, a commoner with an exceptional memory and talent for logic, excelled in academics, particularly in commerce and agriculture. She initially sought marriage to a noble for security but yearned to utilize her talents more broadly. Royle, recognizing their potential, recruits them. Claire is drawn to Royle's promise to eventually confront corrupt nobles and protect the weak, while Cynthia is enticed by the prospect of managing the territory of Kopel, a strategically important southern city.
The group, now consisting of Royle, Yuno, Claire, and Cynthia, embarks on their journey towards Kopel. Royle demonstrates his unique ability to generate "Soldier Units," essentially game-like troops, which shocks Claire and Cynthia. He also reveals his plan to conquer Kopel rather than being appointed as its governor. During their travels, they encounter a bandit leader who attempts to ambush them. Royle, using his ability to generate Soldier Units and Yuno's overwhelming combat prowess, easily defeats the bandits, though he grapples with the moral implications of Yuno being forced to kill.
Further along their journey, Royle continues to train his troops and develop his strategy. He introduces Claire to the various types of Soldier Units available, including spearmen, archers, and cavalry, which greatly expands her tactical options. He also reveals that the "Koon" battle cry of the fox-faced Soldier Units, while amusing, can provide buffs to the troops when uttered by their Princess Unit leader, a mechanic he exploits by having Claire participate in the vocalizations. The group also engages in mundane activities like laundry, where Royle's casual mention of game mechanics and currency further bewilders Cynthia. A mishap during laundry leads to an embarrassing situation for Royle and Cynthia, highlighting the awkwardness and developing relationships within the group.
The chapters conclude with Royle experiencing nightmares, troubled by Yuno's forced participation in combat. Yuno comforts him, reaffirming her loyalty and happiness in being by his side, which seems to alleviate his distress. The group continues their journey, with Royle's ambition to conquer and expand his territory, supported by his unique abilities and loyal companions, driving the narrative forward.