Valkyrie

An ordinary Japanese high-school student named Hatsumi Tarou was having a normal life - preparing for examinations, like all his classmates - when one day everything changed: it was on the day when he saw a talking cat. The cat promptly explained that it was not a cat, but a creature from the Magic World. Once in a thousand or so years, a fighting competition is being held between the best female fighters of the Magic World. The winner becomes the next queen. The referee however should be a human being; and this time, the honor belongs to our friend Tarou!

[Edited from Mobygames]