Go Yoon-ah, who enrolled in a noble school for only the top 1% of students. But due to her mother's remarriage, she suddenly becomes the pinnacle of the school's highest ranking, the 'Platinum', and the younger step-sister of Seung-ho, the school's champion. Yoon-ah, who was ignored because of her poverty, and Seung-ho, arrogant and cold. A precarious relationship that began between two people with different social status and locations. Where exactly will the end of this precarious relationship be?