The narrative picks up in Chapter 3 with the Imperial Army, a direct subordinate unit of the royal family, engaged in an ogre subjugation mission. Their camp is thrown into chaos by the sudden appearance of a Red Dragon. While the ogres are defeated, the dragon's fiery onslaught injures five soldiers and breaks the bones of three swordsmen, leaving only the vice-captain, Konrad, and three mages capable of fighting. Konrad, a seasoned knight with a scar across his face, rushes to inform the unit's commander, a mysterious figure known only as the "Black Knight." This commander, clad in black plate armor and riding a black unicorn named Hayate, is revealed to be a surprisingly laid-back individual, more concerned with bathing than immediate danger. However, his subordinates trust his training implicitly, as his arrival has drastically improved their combat prowess. The Black Knight, with a casual farewell to Konrad, swiftly departs on Hayate to confront the dragon.
Chapter 4 details the Black Knight's arrival at the dragon's location. The three young mages, terrified, are desperately maintaining a protective barrier. The Black Knight arrives with a swift "Dark Shot," knocking the dragon back. He apologizes for his tardiness in a lighthearted manner, which initially frustrates the mages, but his subsequent serious demeanor as he faces the dragon calms them. He dismounts Hayate and, in a display of incredible speed and skill, draws his black katana and, in a single, blindingly fast strike, decapitates the dragon. The dragon's massive head falls, and the Black Knight sheathes his sword, "Sakuya." The soldiers, amazed, celebrate their commander's power. Konrad arrives, concerned about the Black Knight's injuries, which are revealed to be a few broken ribs sustained during the dragon's attack. Hayate, the unicorn, has been using its healing magic to aid the commander. Konrad expresses his reliance on the Black Knight, acknowledging his unique strength in a world facing increasing monster and demon activity. The Black Knight, however, reveals his true motivation: to train his subordinates for an inevitable war with demons, a conflict he believes is imminent after his draw against the Demon King two years prior. He emphasizes the need for his troops to gain combat experience, even if it means taking risks. Konrad pledges his loyalty, and the Black Knight then learns of a Hero summoning in the Holy Kingdom, which causes his demeanor to plummet. He removes his helmet, revealing himself to be a young woman with long black hair and an Eastern appearance, lamenting the arrival of a "harem eroge protagonist."
Chapter 5 shifts focus to Saito Chie, a seemingly ordinary high school girl in modern Japan, who is annoyed by her overly handsome and oblivious childhood friend, Takasugi Yusuke. Yusuke, who unknowingly cultivates a harem of devoted girls, is described as a "real-life eroge protagonist." Chie, a self-proclaimed otaku with survival skills, is constantly bothered by Yusuke's harem and the resulting bullying from his fan club at school. One evening, while walking with Yusuke, a magic circle appears beneath him, and he is summoned to another world. Chie, trying to escape the situation, is accidentally pulled into the summoning circle with him.
Chapter 6 finds Chie waking up in a luxurious room in a place called "Takamagahara," where she meets Amaterasu Omikami, the Sun Goddess of Japanese mythology. Amaterasu explains that Chie died and was brought to this realm because Yusuke's summoning went awry, causing his physical body to collapse. Amaterasu proposes to transfer Chie's soul into a new body in the world of Eldoria, where Yusuke was summoned, to combat the Demon King. Chie, initially hesitant, agrees, and is given a new body, enhanced abilities, and a powerful black katana named "Sakuya" and black armor. She is told her new identity is "Black Knight," and she is sent to a forest near the Imperial capital of Eldoria, four years before Yusuke's summoning.
Chapter 7 begins with Konrad, the Imperial Knight Captain, escorting the Imperial family. They are ambushed by five ogres. Konrad fights valiantly, but is overwhelmed. Suddenly, a black knight on a black unicorn, Hayate, appears and swiftly defeats the remaining ogres. The Black Knight, revealed to be Chie in her new form, helps Konrad and the Imperial family. She then reveals her identity as Chie Saito, a 17-year-old from another world, and is subsequently offered a position in the Imperial Army by Emperor James. Konrad, impressed by her abilities and insight, also pledges his loyalty.
Chapter 8 sees Chie, now the Black Knight, adjusting to her new role. She is appointed Knight Captain and Royal Knight, much to the consternation of other high-ranking officers like Adolf, Celestia, and Adelbert, who are suspicious of her sudden rise and unknown origins. Chie, however, demonstrates her combat prowess by easily subduing them when they question her. She also reveals her deductions about the ongoing kidnapping incidents and the slave auction, identifying a corrupt politician, Bradly Acroyd, as the mastermind.
Chapter 9 continues with Chie, now known as the Black Knight, investigating the kidnapping and slave auction cases. She gathers information from Alice, a maid who serves her, and from the Imperial Army's intelligence. Chie deduces that the kidnappings are a diversion, and the actual victims are being held near the border. She also identifies the culprit as a powerful politician, Bradly Acroyd, who is manipulating the investigation. The chapter ends with Chie and her allies preparing to confront Acroyd.
