Via Google Translate:
Kotoko Tojo is a very ordinary high school girl who exercises, studies, and looks normal. The only thing that isn't typical is that she has a childhood-friend fiancé! Moreover, her partner, Isho Nishizono, is the best handsome prince in school! Kotoko is in a situation which many envy, but for some reason she's desperately hiding the engagement.

The opening of the Doki LOVE Gakuen Romance of the ordinary girls and the prince of the school ♪