After losing both her parents, Nanako grew up living in a temple with other orphaned children, supported by her late father's friend, Seitou. One day, Seitou arranges for her to transfer to Teito Academy, an elite and luxurious school in Tokyo, and she moves into a grand mansion that serves as the school's special dormitory. There she meets Subaru, a handsome but arrogant boy who suddenly kisses her and announces that she is his fiancée. Nanako is shocked and confused by the revelation, especially given Subaru's flirtatious and domineering attitude—he calls himself a prince and behaves as a playboy.

Despite his provocative behavior, Subaru repeatedly comes to Nanako's aid when she faces trouble at school, including bullying from jealous students. As they share the dormitory and attend classes together, Nanako begins to see Subaru's more sincere side and gradually develops feelings for him. Meanwhile, a secret about Nanako's parentage comes to light, complicating her situation further. Just as she decides to embrace her role as Subaru's future bride and accept her place in the influential Tojo family, Subaru unexpectedly asks to break off the engagement. The story follows their emotional struggle and the eventual resolution of their relationship across the three volumes.