Haru, the most exceptional prodigy in the kingdom at the mere age of 16, finds himself enlisted in the prestigious Knight Order. Under the tutelage of Karen-san, a formidable single woman of 29, known as the dreaded 'Oni Knight Leader,' Haru is challenged to banish all self-doubt and brace for the trials ahead. Despite her stern reputation, Karen-san unexpectedly unveils a vulnerable side, confessing her feelings for Haru and revealing a tender demeanor reserved solely for him. As their relationship deepens through shared moments in her chambers and endearing gestures, Haru is torn between duty and the blossoming affection he feels for his superior.