Arashi no Destiny

Hayase Kazuhiro's life was perfectly normal, except that for as long as he can remember, he's had a recurring dream about a princess named Celestia dying the life of her lover, a knight named Arwyth. Kazuhiro's perfectly normal life gets turned upside down, however, when the new transfer student, Fujiki Yoshito, claims to be Arwyth's reincarnation; and if that's not enough, he also says that Kazuhiro is Celestia. The knight-turned-sorcerer has been searching for Celestia for 1300 years, so, to Kazuhiro's dismay, he's not the least bit put off by a silly little thing like gender. Unfortunately, Arwyth isn't the only one who has been searching for Celestia all these centuries. source: https://www.mangaupdates.com/series/wxxubks/arashi-no-destiny