Shoujo Kakumei Utena: Itsuka Kakumei Sareru Monogatari

After meeting a traveling prince who consoled her after the deaths of her parents, Utena Tenjou vowed to become a prince herself. The prince left Utena only with a ring bearing a strange rose crest and a promise that she would meet him again some day.

A few years later, Utena attends Ootori Academy, where she is drawn into a dangerous game. Duelists with rings matching Utena’s own compete for a unique prize: the Rose Bride, Anthy Himemiya, and her mysterious powers. When Utena wins Anthy in a duel, she realizes that if she is to free Anthy and discover the secrets behind Ootori Academy, she has only one option: to revolutionize the world.

Source: TheGamesDB