Jeon Jungkook is a well-respected professor at a prestigious university, known for his strict demeanor and high expectations of his students. One student who catches his attention is a young woman named YN. She is a self-proclaimed badass, unafraid to speak her mind and challenge authority. Her fiery spirit and intelligence intrigue Professor Jungkook, but he also finds her tendency to push boundaries and break rules frustrating. However, their dynamic takes an unexpected turn when YN learns a shocking truth: Professor Jungkook is her stepbrother, a fact that was kept hidden from both of them until now. As they navigate this newfound relationship, they must grapple with their feelings for each other and the ethical implications of their connection.