The Vision of Escaflowne.

High school student Hitomi is transported from Earth to the magical world of Gaea, where she meets boy prince Van Fanel, and is caught up in his quest to unite the countries of Gaea against the ominous Zaibach empire. On the way, she discovers an hidden ability and strives to unravel layers of mystery surrounding Van, his past, and the giant machine known as Escaflowne.