Despite recently turning 17, the otherwise ordinary Yucie still has the body of a child. Having stopped growing past the age of 10, Yucie yearns to fully mature into an adult body. One day, she is chosen as a candidate for the title of "Platinum Princess," given once in a thousand years to whoever is worthy of the Eternal Tiara—a mysterious crown said to grant any wish. She's not alone either, as four other candidates also compete to have their own wishes granted by the crown.

As a result, Yucie enrolls at the nearby Princess Academy in order to grow her heart and work towards becoming qualified for the Eternal Tiara. With her family, rivals, and even the principal of the academy there to lend a hand, will Yucie's much-desired wish finally come true?